diff --git a/build/moz.configure/warnings.configure b/build/moz.configure/warnings.configure
index b9e94d99ba82..d9d08cf32e2f 100644
--- a/build/moz.configure/warnings.configure
+++ b/build/moz.configure/warnings.configure
@@ -98,8 +98,8 @@ check_and_add_gcc_warning('-Wno-error=array-bounds')
 # can't get rid of those PGO warnings
 check_and_add_gcc_warning('-Wno-error=coverage-mismatch', when='MOZ_PGO')
 
-# false positives during PGO
-check_and_add_gcc_warning('-Wno-error=free-nonheap-object', when='MOZ_PGO')
+# false positives depending on optimizations
+check_and_add_gcc_warning('-Wno-error=free-nonheap-object')
 
 # catches format/argument mismatches with printf
 check_and_add_gcc_warning('-Wformat')
diff --git a/old-configure.in b/old-configure.in
index 49bca5071c5f..0c4768b6f223 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -888,7 +888,11 @@ case "$target" in
 *-*linux*)
     if test "$GNU_CC" -o "$GNU_CXX"; then
         MOZ_PGO_OPTIMIZE_FLAGS="-O3"
-        MOZ_OPTIMIZE_FLAGS="-Os"
+        if test -n "$MOZ_DEBUG"; then
+            MOZ_OPTIMIZE_FLAGS="-Os"
+        else
+            MOZ_OPTIMIZE_FLAGS="-O2"
+        fi
         if test -z "$CLANG_CC"; then
            MOZ_OPTIMIZE_FLAGS="-freorder-blocks $MOZ_OPTIMIZE_FLAGS"
         fi