diff --git a/src/type_determiner.cc b/src/type_determiner.cc
index 991bfda..3563634 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 == "fsign") {
+      name == "fabs" || name == "fsign" || name == "floor") {
     if (params.size() != 1) {
       error_ = "incorrect number of parameters for " + name +
                ". Expected 1 got " + std::to_string(params.size());
@@ -599,6 +599,8 @@
       *id = GLSLstd450FAbs;
     } else if (name == "fsign") {
       *id = GLSLstd450FSign;
+    } else if (name == "floor") {
+      *id = GLSLstd450Floor;
     }
 
     return params[0]->result_type();
diff --git a/src/type_determiner_test.cc b/src/type_determiner_test.cc
index d16434d..c2d9155 100644
--- a/src/type_determiner_test.cc
+++ b/src/type_determiner_test.cc
@@ -1592,7 +1592,8 @@
                                                   GLSLstd450RoundEven},
                                          GLSLData{"trunc", GLSLstd450Trunc},
                                          GLSLData{"fabs", GLSLstd450FAbs},
-                                         GLSLData{"fsign", GLSLstd450FSign}));
+                                         GLSLData{"fsign", GLSLstd450FSign},
+                                         GLSLData{"floor", GLSLstd450Floor}));
 
 }  // namespace
 }  // namespace tint