diff --git a/configure.ac b/configure.ac
index 941c52c..c6a1ad9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,7 +31,11 @@ AC_PROG_CC_C99
 AC_PROG_CC_STDC
 
 # Warnings
-AX_COMPILER_FLAGS([], [], [], [-Wall -Wextra -pedantic])
+AX_APPEND_COMPILE_FLAGS([-Wall -Wextra -pedantic])
+AS_IF(
+    [test "x$ax_enable_debug" = "xyes"],
+    [AX_APPEND_COMPILE_FLAGS([-Werror])]
+)
 
 # Use Address-santizer in debug, if it is available
 AS_IF(
diff --git a/src/parse/local.am b/src/parse/local.am
index eede5b3..957c6b4 100644
--- a/src/parse/local.am
+++ b/src/parse/local.am
@@ -24,4 +24,5 @@ BUILT_SOURCES += \
 # Remove problematic warnings from generated files
 libparse_a_CFLAGS = \
     -Wno-switch-default \
+    -Wno-unused-function \
     $(NULL)