diff --git a/configure.ac b/configure.ac
index 4c1a3e5f8..57f824dd0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -235,37 +235,49 @@ WZ_WARNINGS_GCC_CXX="${WZ_Wno_}enum-compare ${WZ_WARNINGS_GCC}"
 if test "x$enable_debug" = "xyes" ; then
 	if test "x$cc_icc" = "xyes" ; then
 		# "-fp-model precise -fp-model source -ftz -no-fma" was here
-		WZ_CFLAGS="${WZ_CFLAGS} -O0 -g -Wcheck -Werror"
-		WZ_CXXFLAGS="${WZ_CXXFLAGS} -O0 -g -Wcheck -Werror"
+		WZ_CFLAGS="${WZ_CFLAGS} -g -Wcheck -Werror"
+		WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -Wcheck -Werror"
 		WZ_CPPFLAGS="${WZ_CPPFLAGS} -DDEBUG"
+		# Override automatic -O2 added by autohell
+		CFLAGS="${CFLAGS} -O0"
+		CXXFLAGS="${CXXFLAGS} -O0"
 	else
-		WZ_CFLAGS="${WZ_CFLAGS} -O0 -g -Werror ${WZ_WARNINGS_GCC_C}"
-		WZ_CXXFLAGS="${WZ_CXXFLAGS} -O0 -g -Werror ${WZ_WARNINGS_GCC_CXX}"
+		WZ_CFLAGS="${WZ_CFLAGS} -g -Werror ${WZ_WARNINGS_GCC_C}"
+		WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -Werror ${WZ_WARNINGS_GCC_CXX}"
 		WZ_C99FLAGS="${WZ_C99FLAGS} -Wno-declaration-after-statement"
 		WZ_CPPFLAGS="${WZ_CPPFLAGS} -DDEBUG"
+		# Override automatic -O2 added by autohell
+		CFLAGS="${CFLAGS} -O0"
+		CXXFLAGS="${CXXFLAGS} -O0"
 	fi
 elif test "x$enable_debug" = "xoptimised" ; then
-	WZ_CFLAGS="${WZ_CFLAGS} -O2 -g -Werror ${WZ_WARNINGS_GCC_C}"
-	WZ_CXXFLAGS="${WZ_CXXFLAGS} -O2 -g -Werror ${WZ_WARNINGS_GCC_CXX}"
+	WZ_CFLAGS="${WZ_CFLAGS} -g -Werror ${WZ_WARNINGS_GCC_C}"
+	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -Werror ${WZ_WARNINGS_GCC_CXX}"
 	WZ_C99FLAGS="${WZ_C99FLAGS} -Wno-declaration-after-statement"
 	WZ_CPPFLAGS="${WZ_CPPFLAGS} -DDEBUG"
 elif test "x$enable_debug" = "xrelaxed" ; then
 	WZ_CFLAGS="${WZ_CFLAGS} -g -O0 ${WZ_WARNINGS_GCC_C}"
-	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -O0 ${WZ_WARNINGS_GCC_CXX}"
+	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g ${WZ_WARNINGS_GCC_CXX}"
 	WZ_CPPFLAGS="${WZ_CPPFLAGS} -DDEBUG"
+	# Override automatic -O2 added by autohell
+	CFLAGS="${CFLAGS} -O0"
+	CXXFLAGS="${CXXFLAGS} -O0"
 elif test "x$enable_debug" = "xdebugprofile" ; then
-	WZ_CFLAGS="${WZ_CFLAGS} -g -O0 -pg ${WZ_WARNINGS_GCC_C}"
-	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -O0 -pg ${WZ_WARNINGS_GCC_CXX}"
+	WZ_CFLAGS="${WZ_CFLAGS} -g -pg ${WZ_WARNINGS_GCC_C}"
+	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -pg ${WZ_WARNINGS_GCC_CXX}"
 	WZ_CPPFLAGS="${WZ_CPPFLAGS} -DDEBUG"
 	LDFLAGS="-pg ${LDFLAGS}"
+	# Override automatic -O2 added by autohell
+	CFLAGS="${CFLAGS} -O0"
+	CXXFLAGS="${CXXFLAGS} -O0"
 elif test "x$enable_debug" = "xprofile" ; then
 	WZ_CFLAGS="${WZ_CFLAGS} -g -Os -pg ${WZ_WARNINGS_GCC_C}"
 	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -Os -pg ${WZ_WARNINGS_GCC_CXX}"
 	WZ_CPPFLAGS="${WZ_CPPFLAGS} -DNDEBUG"
 	LDFLAGS="-pg ${LDFLAGS}"
 elif test "x$enable_debug" = "xg++" ; then
-	WZ_CFLAGS="${WZ_CXXFLAGS} -g -O2 ${WZ_WARNINGS_GCC_CXX}"
-	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g -O2 ${WZ_WARNINGS_GCC_CXX}"
+	WZ_CFLAGS="${WZ_CXXFLAGS} -g ${WZ_WARNINGS_GCC_CXX}"
+	WZ_CXXFLAGS="${WZ_CXXFLAGS} -g ${WZ_WARNINGS_GCC_CXX}"
 	WZ_CPPFLAGS="${WZ_CPPFLAGS} -DDEBUG"
 	CC="g++"
 else