diff --git a/include/clad/Differentiator/BaseForwardModeVisitor.h b/include/clad/Differentiator/BaseForwardModeVisitor.h
index 7b09cc282..375ae88d5 100644
--- a/include/clad/Differentiator/BaseForwardModeVisitor.h
+++ b/include/clad/Differentiator/BaseForwardModeVisitor.h
@@ -56,6 +56,8 @@ class BaseForwardModeVisitor
   StmtDiff VisitCompoundStmt(const clang::CompoundStmt* CS);
   StmtDiff VisitConditionalOperator(const clang::ConditionalOperator* CO);
   StmtDiff VisitCXXBoolLiteralExpr(const clang::CXXBoolLiteralExpr* BL);
+  StmtDiff VisitCharacterLiteral(const clang::CharacterLiteral* CL);
+  StmtDiff VisitStringLiteral(const clang::StringLiteral* SL);
   StmtDiff VisitCXXDefaultArgExpr(const clang::CXXDefaultArgExpr* DE);
   StmtDiff VisitDeclRefExpr(const clang::DeclRefExpr* DRE);
   StmtDiff VisitDeclStmt(const clang::DeclStmt* DS);
diff --git a/lib/Differentiator/BaseForwardModeVisitor.cpp b/lib/Differentiator/BaseForwardModeVisitor.cpp
index 2564683ca..4dc24a7a3 100644
--- a/lib/Differentiator/BaseForwardModeVisitor.cpp
+++ b/lib/Differentiator/BaseForwardModeVisitor.cpp
@@ -1108,7 +1108,7 @@ StmtDiff BaseForwardModeVisitor::VisitCallExpr(const CallExpr* CE) {
         // subexpression.
         if (const auto* MTE = dyn_cast<MaterializeTemporaryExpr>(arg))
           arg = clad_compat::GetSubExpr(MTE);
-        if (!isa<FloatingLiteral>(arg) && !isa<IntegerLiteral>(arg)) {
+        if (!arg->isEvaluatable(m_Context)) {
           allArgsAreConstantLiterals = false;
           break;
         }
@@ -1460,6 +1460,21 @@ BaseForwardModeVisitor::VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr* BL) {
   return StmtDiff(Clone(BL), constant0);
 }
 
+StmtDiff
+BaseForwardModeVisitor::VisitCharacterLiteral(const CharacterLiteral* CL) {
+  llvm::APInt zero(m_Context.getIntWidth(m_Context.IntTy), /*value*/ 0);
+  auto constant0 =
+      IntegerLiteral::Create(m_Context, zero, m_Context.IntTy, noLoc);
+  return StmtDiff(Clone(CL), constant0);
+}
+
+StmtDiff BaseForwardModeVisitor::VisitStringLiteral(const StringLiteral* SL) {
+  llvm::APInt zero(m_Context.getIntWidth(m_Context.IntTy), /*value*/ 0);
+  auto constant0 =
+      IntegerLiteral::Create(m_Context, zero, m_Context.IntTy, noLoc);
+  return StmtDiff(Clone(SL), constant0);
+}
+
 StmtDiff BaseForwardModeVisitor::VisitWhileStmt(const WhileStmt* WS) {
   // begin scope for while loop
   beginScope(Scope::ContinueScope | Scope::BreakScope | Scope::DeclScope |
diff --git a/test/FirstDerivative/CodeGenSimple.C b/test/FirstDerivative/CodeGenSimple.C
index 0759b15a2..02a815c92 100644
--- a/test/FirstDerivative/CodeGenSimple.C
+++ b/test/FirstDerivative/CodeGenSimple.C
@@ -1,4 +1,4 @@
-// RUN: %cladclang %s -I%S/../../include -oCodeGenSimple.out -Xclang -verify 2>&1 | FileCheck %s
+// RUN: %cladclang %s -I%S/../../include -oCodeGenSimple.out 2>&1 | FileCheck %s
 // RUN: ./CodeGenSimple.out | FileCheck -check-prefix=CHECK-EXEC %s
 
 //CHECK-NOT: {{.*error|warning|note:.*}}
@@ -7,7 +7,7 @@
 extern "C" int printf(const char* fmt, ...);
 
 int f_1(int x) {
-   printf("I am being run!\n"); //expected-warning{{attempted to differentiate unsupported statement, no changes applied}} //expected-warning{{function 'printf' was not differentiated because clad failed to differentiate it and no suitable overload was found in namespace 'custom_derivatives', and function may not be eligible for numerical differentiation.}}
+   printf("I am being run!\n");
    return x * x;
 }
 // CHECK: int f_1_darg0(int x) {
diff --git a/test/FirstDerivative/FunctionCallsWithResults.C b/test/FirstDerivative/FunctionCallsWithResults.C
index aa99017fc..f694aaaa3 100644
--- a/test/FirstDerivative/FunctionCallsWithResults.C
+++ b/test/FirstDerivative/FunctionCallsWithResults.C
@@ -170,10 +170,6 @@ double nonRealParamFn(const char* a, const char* b = nullptr) {
   return 1;
 }
 
-// CHECK: clad::ValueAndPushforward<double, double> nonRealParamFn_pushforward(const char *a, const char *b, const char *_d_a, const char *_d_b) {
-// CHECK-NEXT:     return {1, 0};
-// CHECK-NEXT: }
-
 double fn4(double i, double j) {
   double res = nonRealParamFn(0, 0);
   res += i;
@@ -183,9 +179,8 @@ double fn4(double i, double j) {
 // CHECK: double fn4_darg0(double i, double j) {
 // CHECK-NEXT:     double _d_i = 1;
 // CHECK-NEXT:     double _d_j = 0;
-// CHECK-NEXT:     clad::ValueAndPushforward<double, double> _t0 = nonRealParamFn_pushforward(0, 0, 0, 0);
-// CHECK-NEXT:     double _d_res = _t0.pushforward;
-// CHECK-NEXT:     double res = _t0.value;
+// CHECK-NEXT:     double _d_res = 0;
+// CHECK-NEXT:     double res = nonRealParamFn(0, 0);
 // CHECK-NEXT:     _d_res += _d_i;
 // CHECK-NEXT:     res += i;
 // CHECK-NEXT:     return _d_res;
@@ -294,10 +289,21 @@ double sum(double* arr, int n) {
 // CHECK-NEXT:     return {val, _d_val};
 // CHECK-NEXT: }
 
+double check_and_return(double x, char c) {
+  if (c == 'a')
+    return x;
+  return 1;
+}
+// CHECK: clad::ValueAndPushforward<double, double> check_and_return_pushforward(double x, char c, double _d_x, char _d_c) {
+// CHECK-NEXT:   if (c == 'a')
+// CHECK-NEXT:     return {x, _d_x};
+// CHECK-NEXT:   return {1, 0};
+// CHECK-NEXT: }
+
 double fn8(double i, double j) {
   double arr[5] = {};
   modifyArr(arr, 5, i*j);
-  return sum(arr, 5) * std::tanh(1.0);
+  return check_and_return(sum(arr, 5), 'a') * std::tanh(1.0);
 }
 
 // CHECK: double fn8_darg0(double i, double j) {
@@ -307,9 +313,10 @@ double fn8(double i, double j) {
 // CHECK-NEXT:     double arr[5] = {};
 // CHECK-NEXT:     modifyArr_pushforward(arr, 5, i * j, _d_arr, 0, _d_i * j + i * _d_j);
 // CHECK-NEXT:     clad::ValueAndPushforward<double, double> _t0 = sum_pushforward(arr, 5, _d_arr, 0);
-// CHECK-NEXT:     double &_t1 = _t0.value; 
-// CHECK-NEXT:     double _t2 = std::tanh(1.); 
-// CHECK-NEXT:     return _t0.pushforward * _t2 + _t1 * 0; 
+// CHECK-NEXT:     clad::ValueAndPushforward<double, double> _t1 = check_and_return_pushforward(_t0.value, 'a', _t0.pushforward, 0);
+// CHECK-NEXT:     double &_t2 = _t1.value;
+// CHECK-NEXT:     double _t3 = std::tanh(1.);
+// CHECK-NEXT:     return _t1.pushforward * _t3 + _t2 * 0;
 // CHECK-NEXT: }
 
 float test_1_darg0(float x);