diff --git a/configure b/configure
index 55102b0..b152d3a 100755
--- a/configure
+++ b/configure
@@ -11997,14 +11997,14 @@ if test "$crypto_lib" = "none"; then
 $as_echo "none" >&6; }
 else
   if test "$crypto_lib" = "commoncrypto"; then
-    CFLAGS+=" -DSQLCIPHER_CRYPTO_CC"
-    BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_CC"
+    CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_CC"
+    BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_CC"
 	  { $as_echo "$as_me:${as_lineno-$LINENO}: result: commoncrypto" >&5
 $as_echo "commoncrypto" >&6; }
   else
     if test "$crypto_lib" = "libtomcrypt"; then
-      CFLAGS+=" -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
-      BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
+      CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
+      BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
       { $as_echo "$as_me:${as_lineno-$LINENO}: result: libtomcrypt" >&5
 $as_echo "libtomcrypt" >&6; }
       { $as_echo "$as_me:${as_lineno-$LINENO}: checking for register_cipher in -ltomcrypt" >&5
@@ -12056,8 +12056,8 @@ fi
 
     else
       if test "$crypto_lib" = "nss"; then
-        CFLAGS+=" -DSQLCIPHER_CRYPTO_NSS"
-        BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_NSS"
+        CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_NSS"
+        BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_NSS"
         { $as_echo "$as_me:${as_lineno-$LINENO}: result: nss3" >&5
 $as_echo "nss3" >&6; }
         { $as_echo "$as_me:${as_lineno-$LINENO}: checking for PK11_Decrypt in -lnss3" >&5
@@ -12108,8 +12108,8 @@ else
 fi
 
       else
-        CFLAGS+=" -DSQLCIPHER_CRYPTO_OPENSSL"
-        BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_OPENSSL"
+        CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_OPENSSL"
+        BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_OPENSSL"
 	      { $as_echo "$as_me:${as_lineno-$LINENO}: result: openssl" >&5
 $as_echo "openssl" >&6; }
         { $as_echo "$as_me:${as_lineno-$LINENO}: checking for HMAC_Init_ex in -lcrypto" >&5
diff --git a/configure.ac b/configure.ac
index ef21298..b55c935 100644
--- a/configure.ac
+++ b/configure.ac
@@ -203,26 +203,26 @@ if test "$crypto_lib" = "none"; then
   AC_MSG_RESULT([none])
 else
   if test "$crypto_lib" = "commoncrypto"; then
-    CFLAGS+=" -DSQLCIPHER_CRYPTO_CC"
-    BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_CC"
+    CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_CC"
+    BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_CC"
 	  AC_MSG_RESULT([commoncrypto])
   else
     if test "$crypto_lib" = "libtomcrypt"; then
-      CFLAGS+=" -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
-      BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
+      CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
+      BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_LIBTOMCRYPT"
       AC_MSG_RESULT([libtomcrypt])
       AC_CHECK_LIB([tomcrypt], [register_cipher], ,
                    AC_MSG_ERROR([Library crypto not found. Install libtomcrypt!"]))
     else
       if test "$crypto_lib" = "nss"; then
-        CFLAGS+=" -DSQLCIPHER_CRYPTO_NSS"
-        BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_NSS"
+        CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_NSS"
+        BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_NSS"
         AC_MSG_RESULT([nss3])
         AC_CHECK_LIB([nss3], [PK11_Decrypt], ,
                      AC_MSG_ERROR([Library crypto not found. Install nss!"]))
       else
-        CFLAGS+=" -DSQLCIPHER_CRYPTO_OPENSSL"
-        BUILD_CFLAGS+=" -DSQLCIPHER_CRYPTO_OPENSSL"
+        CFLAGS="$CFLAGS -DSQLCIPHER_CRYPTO_OPENSSL"
+        BUILD_CFLAGS="$BUILD_CFLAGS -DSQLCIPHER_CRYPTO_OPENSSL"
 	      AC_MSG_RESULT([openssl])
         AC_CHECK_LIB([crypto], [HMAC_Init_ex], ,
                      AC_MSG_ERROR([Library crypto not found. Install openssl!"]))