diff --git a/src/ctfe.h b/src/ctfe.h
index c584b7cb076f..ff93ba02e92b 100644
--- a/src/ctfe.h
+++ b/src/ctfe.h
@@ -123,7 +123,7 @@ ArrayLiteralExp *createBlockDuplicatedArrayLiteral(Loc loc, Type *type,
 
 /// Create a string literal consisting of 'value' duplicated 'dim' times.
 StringExp *createBlockDuplicatedStringLiteral(Loc loc, Type *type,
-        unsigned value, size_t dim, int sz);
+        unsigned value, size_t dim, unsigned char sz);
 
 
 /* Set dest = src, where both dest and src are container value literals
diff --git a/src/ctfeexpr.c b/src/ctfeexpr.c
index fdeb3876f95d..97f390c84ddf 100644
--- a/src/ctfeexpr.c
+++ b/src/ctfeexpr.c
@@ -489,7 +489,7 @@ ArrayLiteralExp *createBlockDuplicatedArrayLiteral(Loc loc, Type *type,
  * Create a string literal consisting of 'value' duplicated 'dim' times.
  */
 StringExp *createBlockDuplicatedStringLiteral(Loc loc, Type *type,
-        unsigned value, size_t dim, int sz)
+        unsigned value, size_t dim, unsigned char sz)
 {
     utf8_t *s = (utf8_t *)mem.calloc(dim + 1, sz);
     for (size_t elemi = 0; elemi < dim; ++elemi)
diff --git a/src/interpret.c b/src/interpret.c
index af33f68d9f7d..be19875cde92 100644
--- a/src/interpret.c
+++ b/src/interpret.c
@@ -2779,7 +2779,7 @@ Expression *recursivelyCreateArrayLiteral(Loc loc, Type *newtype, InterState *is
         || elemType->ty == Tdchar)
         return createBlockDuplicatedStringLiteral(loc, newtype,
             (unsigned)(elemType->defaultInitLiteral(loc)->toInteger()),
-            len, (int)elemType->size());
+            len, (unsigned char)elemType->size());
     return createBlockDuplicatedArrayLiteral(loc, newtype,
         elemType->defaultInitLiteral(loc),
         len);