diff --git a/compiler/compiler.go b/compiler/compiler.go
index 70951c7a..b4cb5dc8 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -629,6 +629,18 @@ func (c *Compiler) parseFuncDecl(f *ir.Function) *Frame {
 		frame.fn.LLVMFn = llvm.AddFunction(c.mod, name, fnType)
 	}
 
+	// External/exported functions may not retain pointer values.
+	// https://golang.org/cmd/cgo/#hdr-Passing_pointers
+	if f.IsExported() {
+		nocaptureKind := llvm.AttributeKindID("nocapture")
+		nocapture := c.ctx.CreateEnumAttribute(nocaptureKind, 0)
+		for i, typ := range paramTypes {
+			if typ.TypeKind() == llvm.PointerTypeKind {
+				frame.fn.LLVMFn.AddAttributeAtIndex(i+1, nocapture)
+			}
+		}
+	}
+
 	return frame
 }
 
diff --git a/compiler/optimizer.go b/compiler/optimizer.go
index d412b97b..4efea247 100644
--- a/compiler/optimizer.go
+++ b/compiler/optimizer.go
@@ -307,18 +307,6 @@ func (c *Compiler) doesEscape(value llvm.Value) bool {
 				return true
 			}
 		} else if use.IsACallInst() != nilValue {
-			// Call only escapes when the (pointer) parameter is not marked
-			// "nocapture". This flag means that the parameter does not escape
-			// the give function.
-			if use.CalledValue().IsAFunction() != nilValue {
-				if use.CalledValue().IsDeclaration() {
-					// Kind of dirty: assume external functions don't let
-					// pointers escape.
-					// TODO: introduce //go:noescape that sets the 'nocapture'
-					// flag on each input parameter.
-					continue
-				}
-			}
 			if !c.hasFlag(use, value, "nocapture") {
 				return true
 			}