diff --git a/src/type_determiner.cc b/src/type_determiner.cc
index 244c5a4..991bfda 100644
--- a/src/type_determiner.cc
+++ b/src/type_determiner.cc
@@ -577,7 +577,7 @@
   }
 
   if (name == "round" || name == "roundeven" || name == "trunc" ||
-      name == "fabs") {
+      name == "fabs" || name == "fsign") {
     if (params.size() != 1) {
       error_ = "incorrect number of parameters for " + name +
                ". Expected 1 got " + std::to_string(params.size());
@@ -597,6 +597,8 @@
       *id = GLSLstd450Trunc;
     } else if (name == "fabs") {
       *id = GLSLstd450FAbs;
+    } else if (name == "fsign") {
+      *id = GLSLstd450FSign;
     }
 
     return params[0]->result_type();
diff --git a/src/type_determiner_test.cc b/src/type_determiner_test.cc
index 8cb68e1..d16434d 100644
--- a/src/type_determiner_test.cc
+++ b/src/type_determiner_test.cc
@@ -1591,7 +1591,8 @@
                                          GLSLData{"roundeven",
                                                   GLSLstd450RoundEven},
                                          GLSLData{"trunc", GLSLstd450Trunc},
-                                         GLSLData{"fabs", GLSLstd450FAbs}));
+                                         GLSLData{"fabs", GLSLstd450FAbs},
+                                         GLSLData{"fsign", GLSLstd450FSign}));
 
 }  // namespace
 }  // namespace tint