diff --git a/mozilla/configure b/mozilla/configure
index 144b76e27ad..e054ad08766 100755
--- a/mozilla/configure
+++ b/mozilla/configure
@@ -8775,9 +8775,9 @@ fi # SKIP_COMPILER_CHECKS
 # Check whether --with-system-nspr or --without-system-nspr was given.
 if test "${with_system_nspr+set}" = set; then
   withval="$with_system_nspr"
-  if test "$withval" = "no"; then
+  if test "$withval" = "yes"; then
     _USE_SYSTEM_NSPR=1 
-  elif test "$withval" = "yes"; then
+  elif test "$withval" = "no"; then
     :
   else
     { echo "configure: error: Option, system-nspr, does not take an argument ($withval)." 1>&2; exit 1; }
diff --git a/mozilla/configure.in b/mozilla/configure.in
index 510023f11c2..35a33b81a4d 100644
--- a/mozilla/configure.in
+++ b/mozilla/configure.in
@@ -2407,7 +2407,7 @@ dnl ========================================================
 dnl = If NSPR was not detected in the system, 
 dnl = use the one in the source tree (mozilla/nsprpub)
 dnl ========================================================
-MOZ_ARG_WITHOUT_BOOL(system-nspr,
+MOZ_ARG_WITH_BOOL(system-nspr,
 [  --with-system-nspr      Use system installed NSPR],
     _USE_SYSTEM_NSPR=1 )