diff --git a/third_party/lcms/src/cmsopt.c b/third_party/lcms/src/cmsopt.c
index 5ea1b4c85..8a1171820 100644
--- a/third_party/lcms/src/cmsopt.c
+++ b/third_party/lcms/src/cmsopt.c
@@ -104,6 +104,39 @@ typedef struct {
 // Simple optimizations ----------------------------------------------------------------------------------------------------------
 
 
+// Clamp a fixed point integer to signed 28 bits to avoid overflow in
+// calculations.  Clamp is intended for use with colorants, requiring one bit
+// for a colorant and another two bits to avoid overflow when combining the
+// colors.
+cmsINLINE cmsS1Fixed14Number _FixedClamp(cmsS1Fixed14Number n) {
+  const cmsS1Fixed14Number max_positive = 268435455;  // 0x0FFFFFFF;
+  const cmsS1Fixed14Number max_negative = -268435456; // 0xF0000000;
+  // Normally expect the provided number to be in the range [0..1] (but in
+  // fixed 1.14 format), so can perform a quick check for this typical case
+  // to reduce number of compares.
+  const cmsS1Fixed14Number typical_range_mask = 0xFFFF8000;
+
+  if (!(n & typical_range_mask))
+    return n;
+  if (n < max_negative)
+     return max_negative;
+  if (n > max_positive)
+    return max_positive;
+  return n;
+}
+
+// Perform one row of matrix multiply with translation for MatShaperEval16().
+cmsINLINE cmsInt64Number _MatShaperEvaluateRow(cmsS1Fixed14Number* mat,
+                                               cmsS1Fixed14Number off,
+                                               cmsS1Fixed14Number r,
+                                               cmsS1Fixed14Number g,
+                                               cmsS1Fixed14Number b) {
+  return ((cmsInt64Number)mat[0] * r +
+          (cmsInt64Number)mat[1] * g +
+          (cmsInt64Number)mat[2] * b +
+          off + 0x2000) >> 14;
+}
+
 // Remove an element in linked chain
 static
 void _RemoveElement(cmsStage** head)
@@ -1527,7 +1560,8 @@ void MatShaperEval16(register const cmsUInt16Number In[],
                      register const void* D)
 {
     MatShaper8Data* p = (MatShaper8Data*) D;
-    cmsS1Fixed14Number l1, l2, l3, r, g, b;
+    cmsS1Fixed14Number r, g, b;
+    cmsInt64Number l1, l2, l3;
     cmsUInt32Number ri, gi, bi;
 
     // In this case (and only in this case!) we can use this simplification since
@@ -1537,14 +1571,14 @@ void MatShaperEval16(register const cmsUInt16Number In[],
     bi = In[2] & 0xFFU;
 
     // Across first shaper, which also converts to 1.14 fixed point
-    r = p->Shaper1R[ri];
-    g = p->Shaper1G[gi];
-    b = p->Shaper1B[bi];
+    r = _FixedClamp(p->Shaper1R[ri]);
+    g = _FixedClamp(p->Shaper1G[gi]);
+    b = _FixedClamp(p->Shaper1B[bi]);
 
     // Evaluate the matrix in 1.14 fixed point
-    l1 =  (p->Mat[0][0] * r + p->Mat[0][1] * g + p->Mat[0][2] * b + p->Off[0] + 0x2000) >> 14;
-    l2 =  (p->Mat[1][0] * r + p->Mat[1][1] * g + p->Mat[1][2] * b + p->Off[1] + 0x2000) >> 14;
-    l3 =  (p->Mat[2][0] * r + p->Mat[2][1] * g + p->Mat[2][2] * b + p->Off[2] + 0x2000) >> 14;
+    l1 = _MatShaperEvaluateRow(p->Mat[0], p->Off[0], r, g, b);
+    l2 = _MatShaperEvaluateRow(p->Mat[1], p->Off[1], r, g, b);
+    l3 = _MatShaperEvaluateRow(p->Mat[2], p->Off[2], r, g, b);
 
     // Now we have to clip to 0..1.0 range
     ri = (l1 < 0) ? 0 : ((l1 > 16384) ? 16384U : (cmsUInt32Number) l1);