Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -2501,10 +2501,14 @@
 	    [stripped caseInsensitiveCompare: @"INFINITY"] == OF_ORDERED_SAME)
 		return INFINITY;
 	if ([stripped caseInsensitiveCompare: @"-INF"] == OF_ORDERED_SAME ||
 	    [stripped caseInsensitiveCompare: @"-INFINITY"] == OF_ORDERED_SAME)
 		return -INFINITY;
+	if ([stripped caseInsensitiveCompare: @"NAN"] == OF_ORDERED_SAME)
+		return NAN;
+	if ([stripped caseInsensitiveCompare: @"-NAN"] == OF_ORDERED_SAME)
+		return -NAN;
 
 #ifdef HAVE_STRTOF_L
 	const char *UTF8String = self.UTF8String;
 #else
 	/*
@@ -2550,10 +2554,14 @@
 	    [stripped caseInsensitiveCompare: @"INFINITY"] == OF_ORDERED_SAME)
 		return INFINITY;
 	if ([stripped caseInsensitiveCompare: @"-INF"] == OF_ORDERED_SAME ||
 	    [stripped caseInsensitiveCompare: @"-INFINITY"] == OF_ORDERED_SAME)
 		return -INFINITY;
+	if ([stripped caseInsensitiveCompare: @"NAN"] == OF_ORDERED_SAME)
+		return NAN;
+	if ([stripped caseInsensitiveCompare: @"-NAN"] == OF_ORDERED_SAME)
+		return -NAN;
 
 #ifdef HAVE_STRTOD_L
 	const char *UTF8String = self.UTF8String;
 #else
 	/*

Index: tests/OFStringTests.m
==================================================================
--- tests/OFStringTests.m
+++ tests/OFStringTests.m
@@ -1108,11 +1108,12 @@
 	 */
 	TEST(@"-[floatValue]",
 	    C(@"\t-0.25 ").floatValue == -0.25 &&
 	    C(@"\r\n\tINF\t\n").floatValue == INFINITY &&
 	    C(@"\r -INFINITY\n").floatValue == -INFINITY &&
-	    isnan(C(@"   NAN\t\t").floatValue))
+	    isnan(C(@"   NAN\t\t").floatValue) &&
+	    isnan(C(@"   -NaN\t\t").floatValue))
 
 #if !defined(OF_ANDROID) && !defined(OF_SOLARIS) && !defined(OF_DJGPP) && \
     !defined(OF_AMIGAOS_M68K)
 # define INPUT @"\t-0x1.FFFFFFFFFFFFFP-1020 "
 # define EXPECTED -0x1.FFFFFFFFFFFFFP-1020