diff --git a/contrib/ispc.vim b/contrib/ispc.vim
index 4d870dcd..f3cb413b 100644
--- a/contrib/ispc.vim
+++ b/contrib/ispc.vim
@@ -21,6 +21,8 @@ syn keyword	ispcType	export uniform varying int8 int16 int32 int64
 
 "double precision floating point number, with dot, optional exponent
 syn match	cFloat		display contained "\d\+\.\d*d[-+]\=\d*\>"
+"double precision floating point number, starting with dot, optional exponent
+syn match	cFloat		display contained ".\d*d[-+]\=\d*\>"
 "double precision floating point number, without dot, with exponent
 syn match	cFloat		display contained "\d\+d[-+]\=\d\+\>"
 
diff --git a/tests/double-consts.ispc b/tests/double-consts.ispc
index 3259156a..4096aa1c 100644
--- a/tests/double-consts.ispc
+++ b/tests/double-consts.ispc
@@ -7,12 +7,13 @@ export void f_f(uniform float RET[], uniform float aFOO[]) {
     double d1 = 1.0d40;
     double d2 = 1.d40;
     double d3 = 1d40;
-    double d4 = 10000000000000000000000000000000000000000.d;
-    double d5 = 10000000000000000000000000000000000000000.0d;
+    double d4 = .1d41;
+    double d5 = 10000000000000000000000000000000000000000.d;
+    double d6 = 10000000000000000000000000000000000000000.0d;
 
     // All the constants should be equal and if it's evaluated as "float",
     // then sqrt will evaluate to +inf.
-    if (d1 == d2 && d1 == d3 && d1 == d4 && d1 == d5 &&
+    if (d1 == d2 && d1 == d3 && d1 == d4 && d1 == d5 && d1 == d6
         ((float)sqrt(d1)) < 2e20) {
         RET[programIndex] = a;
     }