diff --git a/c b/c
index f76d20b..7c45ce6 100755
--- a/c
+++ b/c
@@ -124,11 +124,20 @@ fi
 comp+=("$CPPFLAGS")
 
 # hash all of our data
-prehash="$CC ${comp[@]}" # compiler + flags and files
+prehash=
+argsprehash="$CC"
 for f in "${comp[@]}"; do
-    [ -f "$f" ] && prehash+="$f $(cpp "$f" 2>&1)"
+    if [ -f "$f" ]; then
+        prehash+=$($hash_func < "$f" | cut -d' ' -f1 2>&1)
+    else
+        # Skip any empty args resulting from extra spaces
+        [ "$f" == "" ] && continue
+        argsprehash+="$f"
+    fi
 done
 
+prehash+=$($hash_func <<< "$argsprehash" | cut -d' ' -f1 2>&1)
+
 # hash everything into one unique identifier, for caching purposes
 id="c$("$hash_func" <<< "$prehash" | cut -d' ' -f1)"
 tmpdir="$tmproot/$id.src"