diff --git a/README.md b/README.md
index e5c0029..b4fd02d 100644
--- a/README.md
+++ b/README.md
@@ -73,7 +73,8 @@ prior to invoking `make`. The following build variables can be configured:
 
  - `CPPFLAGS`: C pre-processor flags, such as externally defined compiler constants.
  
- - `CFLAGS`: Flags to pass onto the C compiler (default: `-Os -Wall`). Note, `-Iinclude` will be added automatically.
+ - `CFLAGS`: Flags to pass onto the C compiler (default: `-Os -Wall -std=c99`). Note, `-Iinclude` will be added 
+   automatically.
    
  - `LDFLAGS`: Linker flags (default is `-lm`).
 
diff --git a/config.mk b/config.mk
index 5eddf24..25954f3 100644
--- a/config.mk
+++ b/config.mk
@@ -21,7 +21,7 @@ CC ?= gcc
 CPPFLAGS += -I$(INC)
 
 # Base compiler options (if not defined externally...)
-CFLAGS ?= -Os -Wall 
+CFLAGS ?= -Os -Wall -std=c99
 
 # Extra warnings (not supported on all compilers)
 #CFLAGS += -Wextra
@@ -31,7 +31,7 @@ LDFLAGS ?= -lm
 
 # cppcheck options for 'check' target
 CHECKOPTS ?= --enable=performance,warning,portability,style --language=c \
-            --error-exitcode=1 $(CHECKEXTRA)
+            --error-exitcode=1 --std=c99 $(CHECKEXTRA)
 
 # Exhaustive checking for newer cppcheck
 #CHECKOPTS += --check-level=exhaustive
diff --git a/src/xchange.c b/src/xchange.c
index b30057d..c98ed55 100644
--- a/src/xchange.c
+++ b/src/xchange.c
@@ -395,7 +395,17 @@ void xZero(void *buf, XType type, int count) {
  *
  */
 char *xStringCopyOf(const char *str) {
-  return str ? strdup(str) : NULL;
+  char *copy;
+  int n;
+
+  if(str == NULL) return NULL;
+
+  n = strlen(str) + 1;
+  copy = (char *) malloc(n);
+  x_check_alloc(copy);
+
+  memcpy(copy, str, n);
+  return copy;
 }
 
 static int TokenMatch(char *a, char *b) {
diff --git a/src/xlookup.c b/src/xlookup.c
index 0144196..93bdba3 100644
--- a/src/xlookup.c
+++ b/src/xlookup.c
@@ -55,7 +55,7 @@ static XLookupEntry *xGetLookupEntryAsync(const XLookupTable *tab, const char *k
 
 static int xLookupPutAsync(XLookupTable *tab, const char *prefix, const XField *field, XField **oldValue) {
   XLookupPrivate *p = (XLookupPrivate *) tab->priv;
-  const char *id = prefix ? xGetAggregateID(prefix, field->name) : strdup(field->name);
+  const char *id = prefix ? xGetAggregateID(prefix, field->name) : xStringCopyOf(field->name);
   long hash = xGetHash(id);
   XLookupEntry *e = xGetLookupEntryAsync(tab, id, hash);
   int idx;