Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -3299,7 +3299,8 @@
     APInt Offset(DL.getTypeStoreSizeInBits(VTy), 0);
     const Value *BV = V->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
 
-    if (Offset.isNonNegative())
+    if (BV->getType()->getPointerElementType()->isSized() &&
+        Offset.isNonNegative())
       if (isDereferenceableFromAttribute(BV, Offset, Ty, DL, CtxI, DT, TLI) &&
           isAligned(BV, Offset, Align, DL))
         return true;
Index: test/Analysis/ValueTracking/memory-dereferenceable.ll
===================================================================
--- test/Analysis/ValueTracking/memory-dereferenceable.ll
+++ test/Analysis/ValueTracking/memory-dereferenceable.ll
@@ -5,6 +5,8 @@
 
 target datalayout = "e"
 
+%TypeOpaque = type opaque
+
 declare zeroext i1 @return_i1()
 
 declare i32* @foo()
@@ -17,6 +19,7 @@
 @globalptr.align1 = external global i8, align 1
 @globalptr.align16 = external global i8, align 16
 
+; CHECK-LABEL: 'test'
 define void @test(i32 addrspace(1)* dereferenceable(8) %dparam,
                   i8 addrspace(1)* dereferenceable(32) align 1 %dparam.align1,
                   i8 addrspace(1)* dereferenceable(32) align 16 %dparam.align16)
@@ -133,6 +136,23 @@
     ret void
 }
 
+; Just check that we don't crash.
+; CHECK-LABEL: 'opaque_type_crasher'
+define void @opaque_type_crasher(%TypeOpaque* dereferenceable(16) %a) {
+entry:
+  %bc = bitcast %TypeOpaque* %a to i8*
+  %ptr8 = getelementptr inbounds i8, i8* %bc, i32 8
+  %ptr32 = bitcast i8* %ptr8 to i32*
+  br i1 undef, label %if.then, label %if.end
+
+if.then:
+  %res = load i32, i32* %ptr32, align 4
+  br label %if.end
+
+if.end:
+  ret void
+}
+
 declare i32 @llvm.experimental.gc.statepoint.p0f_i1f(i64, i32, i1 ()*, i32, i32, ...)
 declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32)