diff --git a/src/compiler.jl b/src/compiler.jl
index 55b67ae92f..6c98ef5a35 100644
--- a/src/compiler.jl
+++ b/src/compiler.jl
@@ -2458,7 +2458,14 @@ function julia_allocator(B, LLVMType, Count, AlignedSize, IsDefault, ZI)
             needs_dynamic_size_workaround = !isa(Size, LLVM.ConstantInt) || convert(Int, Size) != 1
         end
 
-        obj = emit_allocobj!(B, tag, Size, needs_dynamic_size_workaround)
+        T_size_t = convert(LLVM.LLVMType, Int)
+        allocSize = if value_type(Size) != T_size_t
+            trunc!(B, Size, T_size_t)
+        else
+            Size
+        end
+
+        obj = emit_allocobj!(B, tag, allocSize, needs_dynamic_size_workaround)
 
         if ZI != C_NULL
             unsafe_store!(ZI, zero_allocation(B, TT, LLVMType, obj, AlignedSize, Size, #=ZeroAll=#false))