diff --git a/string/obsolete/nsStr.h b/string/obsolete/nsStr.h
index 70c16c5bdb55..28d42a24461d 100644
--- a/string/obsolete/nsStr.h
+++ b/string/obsolete/nsStr.h
@@ -197,6 +197,8 @@ enum  eCharSize {eOneByte=0,eTwoByte=1};
 #define kRadix16        (16)
 #define kAutoDetect     (100)
 #define kRadixUnknown   (kAutoDetect+1)
+#define IGNORE_CASE     (PR_TRUE)
+
 const   PRInt32 kDefaultStringSize = 64;
 const   PRInt32 kNotFound = -1;
 
diff --git a/xpcom/ds/nsStr.h b/xpcom/ds/nsStr.h
index 70c16c5bdb55..28d42a24461d 100644
--- a/xpcom/ds/nsStr.h
+++ b/xpcom/ds/nsStr.h
@@ -197,6 +197,8 @@ enum  eCharSize {eOneByte=0,eTwoByte=1};
 #define kRadix16        (16)
 #define kAutoDetect     (100)
 #define kRadixUnknown   (kAutoDetect+1)
+#define IGNORE_CASE     (PR_TRUE)
+
 const   PRInt32 kDefaultStringSize = 64;
 const   PRInt32 kNotFound = -1;
 
diff --git a/xpcom/string/obsolete/nsStr.h b/xpcom/string/obsolete/nsStr.h
index 70c16c5bdb55..28d42a24461d 100644
--- a/xpcom/string/obsolete/nsStr.h
+++ b/xpcom/string/obsolete/nsStr.h
@@ -197,6 +197,8 @@ enum  eCharSize {eOneByte=0,eTwoByte=1};
 #define kRadix16        (16)
 #define kAutoDetect     (100)
 #define kRadixUnknown   (kAutoDetect+1)
+#define IGNORE_CASE     (PR_TRUE)
+
 const   PRInt32 kDefaultStringSize = 64;
 const   PRInt32 kNotFound = -1;