diff --git a/docs/capi.rst b/docs/capi.rst
index 104262bde1..245bcca862 100644
--- a/docs/capi.rst
+++ b/docs/capi.rst
@@ -69,10 +69,14 @@ However, if you want to fetch the imported rules from another source (eg: from a
 database or remote service), a callback function can be set with
 :c:func:`yr_compiler_set_include_callback`.
 The callback receives the following parameters:
- *``include_name``: name of the requested file.
- *``calling_rule_filename``: the requesting file name (NULL if not a file).
- *``calling_rule_namespace``: namespace (NULL if undefined).
-And should return the requested file as a string.
+ * ``include_name``: name of the requested file.
+ * ``calling_rule_filename``: the requesting file name (NULL if not a file).
+ * ``calling_rule_namespace``: namespace (NULL if undefined).
+ * ``user_data`` pointer is the same you passed to
+ :c:func:`yr_compiler_set_include_callback`.
+It should return the requested file's content as a string. The memory for this string
+should be allocated by the callback function (yr_malloc can be used) but will
+be automatically freed by the yara compiler.
 
 The callback function has the following prototype:
 
@@ -695,6 +699,31 @@ Functions
   Enables the specified rule. After being disabled with :c:func:`yr_rule_disable`
   a rule can be enabled again by using this function.
 
+.. c:function:: void* yr_calloc(size_t count, size_t size);
+
+  Cross-platform wrapper for HeapAlloc on Windows and calloc on other platforms.
+
+.. c:function:: void* yr_malloc(size_t size);
+
+  Cross-platform wrapper for HeapAlloc on Windows and malloc on other platforms.
+
+.. c:function:: void* yr_realloc(void* ptr, size_t size);
+
+  Cross-platform wrapper for HeapReAlloc on Windows and realloc on other platforms.
+
+.. c:function:: void yr_free(void* ptr);
+
+  Cross-platform wrapper for HeapFree on Windows and free on other platforms.
+
+.. c:function:: char* yr_strdup(const char *str);
+
+  Allocates a new buffer the same size as str and copies str to the new buffer.
+
+.. c:function:: char* yr_strdup(const char *str, size_t n);
+
+  Allocates a new buffer of size n and copies the n first character of str.
+
+
 Error codes
 -----------
 
diff --git a/libyara/compiler.c b/libyara/compiler.c
index a7e4ca5119..f405ec3574 100644
--- a/libyara/compiler.c
+++ b/libyara/compiler.c
@@ -189,7 +189,7 @@ YR_API void yr_compiler_set_include_callback(
     void* user_data)
 {
   compiler->include_callback = include_callback;
-  compiler->user_data = user_data;
+  compiler->incl_clbk_user_data = user_data;
 }
 
 
diff --git a/libyara/include/yara.h b/libyara/include/yara.h
index 3a35518663..a627e90bf9 100644
--- a/libyara/include/yara.h
+++ b/libyara/include/yara.h
@@ -39,5 +39,6 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "yara/error.h"
 #include "yara/stream.h"
 #include "yara/hash.h"
+#include "yara/mem.h"
 
 #endif
diff --git a/libyara/include/yara/compiler.h b/libyara/include/yara/compiler.h
index 93a6263cc8..5302442311 100644
--- a/libyara/include/yara/compiler.h
+++ b/libyara/include/yara/compiler.h
@@ -121,6 +121,7 @@ typedef struct _YR_COMPILER
 
   char              include_base_dir[MAX_PATH];
   void*             user_data;
+  void*             incl_clbk_user_data;
 
   YR_COMPILER_CALLBACK_FUNC  callback;
   YR_COMPILER_INCLUDE_CALLBACK_FUNC include_callback;
diff --git a/libyara/include/yara/mem.h b/libyara/include/yara/mem.h
index ff7dc3ec7e..a556fcb583 100644
--- a/libyara/include/yara/mem.h
+++ b/libyara/include/yara/mem.h
@@ -31,6 +31,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define YR_MEM_H
 
 #include <stdio.h>
+#include <yara/utils.h>
 
 #ifdef DMALLOC
 
@@ -45,24 +46,24 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #else
 
-void* yr_calloc(
+YR_API void* yr_calloc(
     size_t count,
     size_t size);
 
-void* yr_malloc(
+YR_API void* yr_malloc(
     size_t size);
 
-void* yr_realloc(
+YR_API void* yr_realloc(
     void* ptr,
     size_t size);
 
-void yr_free(
+YR_API void yr_free(
     void *ptr);
 
-char* yr_strdup(
+YR_API char* yr_strdup(
     const char *str);
 
-char* yr_strndup(
+YR_API char* yr_strndup(
 	const char *str, size_t n);
 
 #endif
diff --git a/libyara/lexer.c b/libyara/lexer.c
index b5d9108b21..68fd25b268 100644
--- a/libyara/lexer.c
+++ b/libyara/lexer.c
@@ -1458,10 +1458,20 @@ YY_RULE_SETUP
     }
     else
     {
-      const char* res = compiler->include_callback(yyextra->lex_buf, current_file_name, compiler->current_namespace->name, compiler->user_data);
+      const char* res = compiler->include_callback(
+                                              yyextra->lex_buf,
+                                              current_file_name,
+                                              compiler->current_namespace->name,
+                                              compiler->incl_clbk_user_data);
+
       if (res != NULL)
       {
-        int error_code = _yr_compiler_push_file_name(compiler, yyextra->lex_buf);
+        const char* res_dup = yr_strdup(res);
+        yr_free((void*) res);
+        res = NULL;
+
+        int error_code = _yr_compiler_push_file_name( compiler,
+                                                      yyextra->lex_buf);
 
         if (error_code != ERROR_SUCCESS)
         {
@@ -1474,16 +1484,24 @@ YY_RULE_SETUP
             yyerror(yyscanner, compiler, "includes depth exceeded");
           }
 
+          yr_free((void*) res_dup);
+          res_dup = NULL;
           yyterminate();
         }
+
         // Workaround for flex issue: https://github.com/westes/flex/issues/58
         yara_yypush_buffer_state(YY_CURRENT_BUFFER,yyscanner);
-        yara_yy_scan_string(res,yyscanner);
+        yara_yy_scan_string(res_dup,yyscanner);
+
+        yr_free((void*) res_dup);
+        res_dup = NULL;
       }
       else
       {
-        snprintf(buffer, sizeof(buffer),
-                 "'include_callback' failed to return rules contained in '%s'", yyextra->lex_buf);
+        snprintf( buffer,
+                  sizeof(buffer),
+                  "'include_callback' failed to return rules contained in '%s'",
+                  yyextra->lex_buf);
         yyerror(yyscanner, compiler, buffer);
       }
 
@@ -1503,7 +1521,7 @@ case YY_STATE_EOF(str):
 case YY_STATE_EOF(regexp):
 case YY_STATE_EOF(include):
 case YY_STATE_EOF(comment):
-#line 336 "lexer.l"
+#line 354 "lexer.l"
 {
 
   YR_COMPILER* compiler = yara_yyget_extra(yyscanner);
@@ -1539,7 +1557,7 @@ case YY_STATE_EOF(comment):
 	YY_BREAK
 case 44:
 YY_RULE_SETUP
-#line 370 "lexer.l"
+#line 388 "lexer.l"
 {
 
   yylval->c_string = yr_strdup(yytext);
@@ -1555,7 +1573,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 45:
 YY_RULE_SETUP
-#line 384 "lexer.l"
+#line 402 "lexer.l"
 {
 
   yylval->c_string = yr_strdup(yytext);
@@ -1571,7 +1589,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 46:
 YY_RULE_SETUP
-#line 398 "lexer.l"
+#line 416 "lexer.l"
 {
 
   yylval->c_string = yr_strdup(yytext);
@@ -1588,7 +1606,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 47:
 YY_RULE_SETUP
-#line 413 "lexer.l"
+#line 431 "lexer.l"
 {
 
   yylval->c_string = yr_strdup(yytext);
@@ -1605,7 +1623,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 48:
 YY_RULE_SETUP
-#line 428 "lexer.l"
+#line 446 "lexer.l"
 {
 
   yylval->c_string = yr_strdup(yytext);
@@ -1622,7 +1640,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 49:
 YY_RULE_SETUP
-#line 443 "lexer.l"
+#line 461 "lexer.l"
 {
 
   char* text = yytext;
@@ -1663,7 +1681,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 50:
 YY_RULE_SETUP
-#line 482 "lexer.l"
+#line 500 "lexer.l"
 {
 
   if (strlen(yytext) > 128)
@@ -1684,7 +1702,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 51:
 YY_RULE_SETUP
-#line 501 "lexer.l"
+#line 519 "lexer.l"
 {
 
   #ifdef _MSC_VER
@@ -1706,7 +1724,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 52:
 YY_RULE_SETUP
-#line 520 "lexer.l"
+#line 538 "lexer.l"
 {
   yylval->double_ = atof(yytext);
   return _DOUBLE_;
@@ -1714,7 +1732,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 53:
 YY_RULE_SETUP
-#line 525 "lexer.l"
+#line 543 "lexer.l"
 {
   yylval->integer = xtoi(yytext + 2);
   return _NUMBER_;
@@ -1722,7 +1740,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 54:
 YY_RULE_SETUP
-#line 530 "lexer.l"
+#line 548 "lexer.l"
 {
   yylval->integer = otoi(yytext + 2);
   return _NUMBER_;
@@ -1730,7 +1748,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 55:
 YY_RULE_SETUP
-#line 536 "lexer.l"
+#line 554 "lexer.l"
 {     /* saw closing quote - all done */
 
   ALLOC_SIZED_STRING(s, yyextra->lex_buf_len);
@@ -1746,7 +1764,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 56:
 YY_RULE_SETUP
-#line 550 "lexer.l"
+#line 568 "lexer.l"
 {
 
   LEX_CHECK_SPACE_OK("\t", yyextra->lex_buf_len, LEX_BUF_SIZE);
@@ -1756,7 +1774,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 57:
 YY_RULE_SETUP
-#line 558 "lexer.l"
+#line 576 "lexer.l"
 {
 
   LEX_CHECK_SPACE_OK("\n", yyextra->lex_buf_len, LEX_BUF_SIZE);
@@ -1766,7 +1784,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 58:
 YY_RULE_SETUP
-#line 566 "lexer.l"
+#line 584 "lexer.l"
 {
 
   LEX_CHECK_SPACE_OK("\"", yyextra->lex_buf_len, LEX_BUF_SIZE);
@@ -1776,7 +1794,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 59:
 YY_RULE_SETUP
-#line 574 "lexer.l"
+#line 592 "lexer.l"
 {
 
   LEX_CHECK_SPACE_OK("\\", yyextra->lex_buf_len, LEX_BUF_SIZE);
@@ -1786,7 +1804,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 60:
 YY_RULE_SETUP
-#line 582 "lexer.l"
+#line 600 "lexer.l"
 {
 
    int result;
@@ -1799,13 +1817,13 @@ YY_RULE_SETUP
 	YY_BREAK
 case 61:
 YY_RULE_SETUP
-#line 593 "lexer.l"
+#line 611 "lexer.l"
 { YYTEXT_TO_BUFFER; }
 	YY_BREAK
 case 62:
 /* rule 62 can match eol */
 YY_RULE_SETUP
-#line 596 "lexer.l"
+#line 614 "lexer.l"
 {
 
   yyerror(yyscanner, compiler, "unterminated string");
@@ -1815,7 +1833,7 @@ YY_RULE_SETUP
 case 63:
 /* rule 63 can match eol */
 YY_RULE_SETUP
-#line 602 "lexer.l"
+#line 620 "lexer.l"
 {
 
   yyerror(yyscanner, compiler, "illegal escape sequence");
@@ -1824,7 +1842,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 64:
 YY_RULE_SETUP
-#line 609 "lexer.l"
+#line 627 "lexer.l"
 {
 
   if (yyextra->lex_buf_len > 0)
@@ -1853,7 +1871,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 65:
 YY_RULE_SETUP
-#line 636 "lexer.l"
+#line 654 "lexer.l"
 {
 
   LEX_CHECK_SPACE_OK("/", yyextra->lex_buf_len, LEX_BUF_SIZE);
@@ -1863,7 +1881,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 66:
 YY_RULE_SETUP
-#line 644 "lexer.l"
+#line 662 "lexer.l"
 {
 
   LEX_CHECK_SPACE_OK("\\.", yyextra->lex_buf_len, LEX_BUF_SIZE);
@@ -1881,13 +1899,13 @@ YY_RULE_SETUP
 	YY_BREAK
 case 67:
 YY_RULE_SETUP
-#line 660 "lexer.l"
+#line 678 "lexer.l"
 { YYTEXT_TO_BUFFER; }
 	YY_BREAK
 case 68:
 /* rule 68 can match eol */
 YY_RULE_SETUP
-#line 663 "lexer.l"
+#line 681 "lexer.l"
 {
 
   yyerror(yyscanner, compiler, "unterminated regular expression");
@@ -1896,7 +1914,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 69:
 YY_RULE_SETUP
-#line 670 "lexer.l"
+#line 688 "lexer.l"
 {
 
   yyextra->lex_buf_ptr = yyextra->lex_buf;
@@ -1906,7 +1924,7 @@ YY_RULE_SETUP
 	YY_BREAK
 case 70:
 YY_RULE_SETUP
-#line 678 "lexer.l"
+#line 696 "lexer.l"
 {
 
   yyextra->lex_buf_ptr = yyextra->lex_buf;
@@ -1917,7 +1935,7 @@ YY_RULE_SETUP
 case 71:
 /* rule 71 can match eol */
 YY_RULE_SETUP
-#line 686 "lexer.l"
+#line 704 "lexer.l"
 {
   // Match hex-digits with whitespace or comments. The latter are stripped
   // out by hex_lexer.l
@@ -1933,12 +1951,12 @@ YY_RULE_SETUP
 case 72:
 /* rule 72 can match eol */
 YY_RULE_SETUP
-#line 699 "lexer.l"
+#line 717 "lexer.l"
 /* skip whitespace */
 	YY_BREAK
 case 73:
 YY_RULE_SETUP
-#line 701 "lexer.l"
+#line 719 "lexer.l"
 {
 
   if (yytext[0] >= 32 && yytext[0] < 127)
@@ -1954,10 +1972,10 @@ YY_RULE_SETUP
 	YY_BREAK
 case 74:
 YY_RULE_SETUP
-#line 714 "lexer.l"
+#line 732 "lexer.l"
 ECHO;
 	YY_BREAK
-#line 1961 "lexer.c"
+#line 1979 "lexer.c"
 
 	case YY_END_OF_BUFFER:
 		{
@@ -3106,7 +3124,7 @@ void yara_yyfree (void * ptr , yyscan_t yyscanner)
 
 #define YYTABLES_NAME "yytables"
 
-#line 714 "lexer.l"
+#line 732 "lexer.l"
 
 
 
diff --git a/libyara/lexer.l b/libyara/lexer.l
index d4a29d65c2..84830f7453 100644
--- a/libyara/lexer.l
+++ b/libyara/lexer.l
@@ -292,10 +292,20 @@ include[ \t]+\"         {
     }
     else
     {
-      const char* res = compiler->include_callback(yyextra->lex_buf, current_file_name, compiler->current_namespace->name, compiler->user_data);
+      const char* res = compiler->include_callback(
+                                              yyextra->lex_buf,
+                                              current_file_name,
+                                              compiler->current_namespace->name,
+                                              compiler->incl_clbk_user_data);
+
       if (res != NULL)
       {
-        int error_code = _yr_compiler_push_file_name(compiler, yyextra->lex_buf);
+        const char* res_dup = yr_strdup(res);
+        yr_free((void*) res);
+        res = NULL;
+
+        int error_code = _yr_compiler_push_file_name( compiler,
+                                                      yyextra->lex_buf);
 
         if (error_code != ERROR_SUCCESS)
         {
@@ -308,16 +318,24 @@ include[ \t]+\"         {
             yyerror(yyscanner, compiler, "includes depth exceeded");
           }
 
+          yr_free((void*) res_dup);
+          res_dup = NULL;
           yyterminate();
         }
+
         // Workaround for flex issue: https://github.com/westes/flex/issues/58
         yypush_buffer_state(YY_CURRENT_BUFFER, yyscanner);
-        yy_scan_string(res, yyscanner);
+        yy_scan_string(res_dup, yyscanner);
+
+        yr_free((void*) res_dup);
+        res_dup = NULL;
       }
       else
       {
-        snprintf(buffer, sizeof(buffer),
-                 "'include_callback' failed to return rules contained in '%s'", yyextra->lex_buf);
+        snprintf( buffer,
+                  sizeof(buffer),
+                  "'include_callback' failed to return rules contained in '%s'",
+                  yyextra->lex_buf);
         yyerror(yyscanner, compiler, buffer);
       }
 
diff --git a/libyara/mem.c b/libyara/mem.c
index 53a151fe69..55b0d8acca 100644
--- a/libyara/mem.c
+++ b/libyara/mem.c
@@ -27,7 +27,7 @@ ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-
+#include <yara/utils.h>
 
 #if defined(_WIN32) || defined(__CYGWIN__)
 
@@ -58,31 +58,31 @@ int yr_heap_free(void)
 }
 
 
-void* yr_calloc(size_t count, size_t size)
+YR_API void* yr_calloc(size_t count, size_t size)
 {
   return (void*) HeapAlloc(hHeap, HEAP_ZERO_MEMORY, count * size);
 }
 
 
-void* yr_malloc(size_t size)
+YR_API void* yr_malloc(size_t size)
 {
   return (void*) HeapAlloc(hHeap, HEAP_ZERO_MEMORY, size);
 }
 
 
-void* yr_realloc(void* ptr, size_t size)
+YR_API void* yr_realloc(void* ptr, size_t size)
 {
   return (void*) HeapReAlloc(hHeap, HEAP_ZERO_MEMORY, ptr, size);
 }
 
 
-void yr_free(void* ptr)
+YR_API void yr_free(void* ptr)
 {
   HeapFree(hHeap, 0, ptr);
 }
 
 
-char* yr_strdup(const char *str)
+YR_API char* yr_strdup(const char *str)
 {
   size_t len = strlen(str);
   char *dup = (char*) yr_malloc(len + 1);
@@ -97,7 +97,7 @@ char* yr_strdup(const char *str)
 }
 
 
-char* yr_strndup(const char *str, size_t n)
+YR_API char* yr_strndup(const char *str, size_t n)
 {
   size_t len = strnlen(str, n);
   char *dup = (char*) yr_malloc(len + 1);
@@ -133,37 +133,37 @@ int yr_heap_free(void)
 }
 
 
-void* yr_calloc(size_t count, size_t size)
+YR_API void* yr_calloc(size_t count, size_t size)
 {
   return calloc(count, size);
 }
 
 
-void* yr_malloc(size_t size)
+YR_API void* yr_malloc(size_t size)
 {
   return malloc(size);
 }
 
 
-void* yr_realloc(void* ptr, size_t size)
+YR_API void* yr_realloc(void* ptr, size_t size)
 {
   return realloc(ptr, size);
 }
 
 
-void yr_free(void *ptr)
+YR_API void yr_free(void *ptr)
 {
   free(ptr);
 }
 
 
-char* yr_strdup(const char *str)
+YR_API char* yr_strdup(const char *str)
 {
   return strdup(str);
 }
 
 
-char* yr_strndup(const char *str, size_t n)
+YR_API char* yr_strndup(const char *str, size_t n)
 {
   return strndup(str, n);
 }