diff --git a/.github/workflows/ci-build.yml b/.github/workflows/ci-build.yml
index 46120cf8..30d99dc6 100644
--- a/.github/workflows/ci-build.yml
+++ b/.github/workflows/ci-build.yml
@@ -11,10 +11,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Configure
-        # We enforce -Wdeclaration-after-statement because Qt project needs to
-        # build MD4C with Integrity compiler which chokes whenever a declaration
-        # is not at the beginning of a block.
-        run: CFLAGS='--coverage -g -O0 -Wall -Wdeclaration-after-statement -Werror' cmake -DCMAKE_BUILD_TYPE=Debug -G 'Unix Makefiles' .
+        run: CFLAGS='--coverage -Werror' cmake -DCMAKE_BUILD_TYPE=Debug -G 'Unix Makefiles' .
       - name: Build
         run: make VERBOSE=1
       - name: Test
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 82fdf688..84648996 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -41,7 +41,12 @@ endif()
 
 
 if(${CMAKE_C_COMPILER_ID} MATCHES GNU|Clang)
-    add_compile_options(-Wall -Wextra)
+    add_compile_options(-Wall -Wextra -Wshadow)
+
+    # We enforce -Wdeclaration-after-statement because Qt project needs to
+    # build MD4C with Integrity compiler which chokes whenever a declaration
+    # is not at the beginning of a block.
+    add_compile_options(-Wdeclaration-after-statement)
 elseif(MSVC)
     # Disable warnings about the so-called unsecured functions:
     add_definitions(/D_CRT_SECURE_NO_WARNINGS)
diff --git a/src/md4c.c b/src/md4c.c
index 7c397106..d34933f7 100644
--- a/src/md4c.c
+++ b/src/md4c.c
@@ -4201,6 +4201,7 @@ md_process_inlines(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
     MD_MARK* mark;
     OFF off = lines[0].beg;
     OFF end = lines[n_lines-1].end;
+    OFF tmp;
     int enforce_hardbreak = 0;
     int ret = 0;
 
@@ -4216,7 +4217,7 @@ md_process_inlines(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
 
     while(1) {
         /* Process the text up to the next mark or end-of-line. */
-        OFF tmp = (line->end < mark->beg ? line->end : mark->beg);
+        tmp = (line->end < mark->beg ? line->end : mark->beg);
         if(tmp > off) {
             MD_TEXT(text_type, STR(off), tmp - off);
             off = tmp;
@@ -4427,8 +4428,6 @@ md_process_inlines(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
                 break;
 
             if(text_type == MD_TEXT_CODE || text_type == MD_TEXT_LATEXMATH) {
-                OFF tmp;
-
                 MD_ASSERT(prev_mark != NULL);
                 MD_ASSERT(ISANYOF2_(prev_mark->ch, '`', '$')  &&  (prev_mark->flags & MD_MARK_OPENER));
                 MD_ASSERT(ISANYOF2_(mark->ch, '`', '$')  &&  (mark->flags & MD_MARK_CLOSER));
@@ -4447,8 +4446,7 @@ md_process_inlines(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
             } else if(text_type == MD_TEXT_HTML) {
                 /* Inside raw HTML, we output the new line verbatim, including
                  * any trailing spaces. */
-                OFF tmp = off;
-
+                tmp = off;
                 while(tmp < end  &&  ISBLANK(tmp))
                     tmp++;
                 if(tmp > off)