diff --git a/contrib/ispc.vim b/contrib/ispc.vim
index cc8493f0..4d870dcd 100644
--- a/contrib/ispc.vim
+++ b/contrib/ispc.vim
@@ -19,6 +19,11 @@ syn keyword	ispcRepeat	cdo cfor cwhile
 syn keyword	ispcBuiltin	programCount programIndex	
 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, without dot, with exponent
+syn match	cFloat		display contained "\d\+d[-+]\=\d\+\>"
+
 " Default highlighting
 command -nargs=+ HiLink hi def link <args>
 HiLink ispcStatement	Statement
diff --git a/docs/ispc.rst b/docs/ispc.rst
index ff07f6d8..224faaa9 100644
--- a/docs/ispc.rst
+++ b/docs/ispc.rst
@@ -270,6 +270,14 @@ new reserved words: ``unmasked``, ``foreach_unique``, ``foreach_active``,
 and ``in``.  Any program that happens to have a variable or function with
 one of these names must be modified to rename that symbol.
 
+Updating ISPC Programs For Changes In ISPC 1.4.5
+----------------------------------------------
+
+This release adds support for double precision floating point constants.
+Double precision floating point constants are floating point number with
+``d`` suffix and optional exponent part. Here are some examples: 3.14d,
+31.4d-1, 1.d, 1.0d, 1d-2. Note that floating point number without suffix is
+treated as single precision constant.
 
 Getting Started with ISPC
 =========================
@@ -1349,7 +1357,8 @@ but are likely to be supported in future releases:
 * Bitfield members of ``struct`` types
 * Variable numbers of arguments to functions
 * Literal floating-point constants (even without a ``f`` suffix) are
-  currently treated as being ``float`` type, not ``double``
+  currently treated as being ``float`` type, not ``double``. To have a double
+  precision floating point constant use ``d`` suffix.
 * The ``volatile`` qualifier
 * The ``register`` storage class for variables.  (Will be ignored).
 
diff --git a/tests/double-consts.ispc b/tests/double-consts.ispc
new file mode 100644
index 00000000..3259156a
--- /dev/null
+++ b/tests/double-consts.ispc
@@ -0,0 +1,23 @@
+
+export uniform int width() { return programCount; }
+
+export void f_f(uniform float RET[], uniform float aFOO[]) {
+    double a = aFOO[programIndex];
+    // Test parsing of double constants.
+    double d1 = 1.0d40;
+    double d2 = 1.d40;
+    double d3 = 1d40;
+    double d4 = 10000000000000000000000000000000000000000.d;
+    double d5 = 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 &&
+        ((float)sqrt(d1)) < 2e20) {
+        RET[programIndex] = a;
+    }
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 1 + programIndex;
+}