diff --git a/include/libspirv/libspirv.h b/include/libspirv/libspirv.h
index 6f88b1c6..60007c45 100644
--- a/include/libspirv/libspirv.h
+++ b/include/libspirv/libspirv.h
@@ -362,6 +362,7 @@ typedef struct spv_position_t {
 typedef struct spv_diagnostic_t {
   spv_position_t position;
   char *error;
+  bool isTextSource;
 } spv_diagnostic_t;
 
 // Type Definitions
diff --git a/source/diagnostic.cpp b/source/diagnostic.cpp
index a6f87aa6..1f51b39a 100644
--- a/source/diagnostic.cpp
+++ b/source/diagnostic.cpp
@@ -42,6 +42,7 @@ spv_diagnostic spvDiagnosticCreate(const spv_position position,
   diagnostic->error = new char[length];
   spvCheck(!diagnostic->error, delete diagnostic; return nullptr);
   diagnostic->position = *position;
+  diagnostic->isTextSource = false;
   memset(diagnostic->error, 0, length);
   strncpy(diagnostic->error, message, length);
   return diagnostic;
@@ -58,10 +59,7 @@ void spvDiagnosticDestroy(spv_diagnostic diagnostic) {
 spv_result_t spvDiagnosticPrint(const spv_diagnostic diagnostic) {
   spvCheck(!diagnostic, return SPV_ERROR_INVALID_DIAGNOSTIC);
 
-  // TODO: Check that the logic choosing between a text or binary diagnostic is
-  // corrent.
-  if ((diagnostic->position.line || diagnostic->position.column) &&
-      diagnostic->position.index) {
+  if (diagnostic->isTextSource) {
     // NOTE: This is a text position
     // NOTE: add 1 to the line as editors start at line 1, we are counting new
     // line characters to start at line 0
@@ -69,9 +67,8 @@ spv_result_t spvDiagnosticPrint(const spv_diagnostic diagnostic) {
               << diagnostic->position.column + 1 << ": " << diagnostic->error
               << "\n";
     return SPV_SUCCESS;
-  } else if (!diagnostic->position.line && !diagnostic->position.column &&
-             diagnostic->position.index) {
-    // NOTE: This is a binary position
+  } else {
+    // NOTE: Assume this is a binary position
     std::cerr << "error: " << diagnostic->position.index << ": "
               << diagnostic->error << "\n";
     return SPV_SUCCESS;
diff --git a/source/text.cpp b/source/text.cpp
index 4fefcfd8..d06c55c3 100644
--- a/source/text.cpp
+++ b/source/text.cpp
@@ -186,8 +186,10 @@ spv_result_t spvTextWordGet(const spv_text text,
   }
 }
 
+namespace {
+
 // Returns true if the string at the given position in text starts with "Op".
-static bool spvStartsWithOp(const spv_text text, const spv_position position) {
+bool spvStartsWithOp(const spv_text text, const spv_position position) {
   if (text->length < position->index + 3) return false;
   char ch0 = text->str[position->index];
   char ch1 = text->str[position->index + 1];
@@ -195,6 +197,8 @@ static bool spvStartsWithOp(const spv_text text, const spv_position position) {
   return ('O' == ch0 && 'p' == ch1 && ('A' <= ch2 && ch2 <= 'Z'));
 }
 
+} // anonymous namespace
+
 // Returns true if a new instruction begins at the given position in text.
 bool spvTextIsStartOfNewInst(const spv_text text,
                              const spv_position position) {
@@ -670,11 +674,17 @@ spv_result_t spvTextEncodeOpcode(
   return SPV_SUCCESS;
 }
 
-spv_result_t spvTextToBinary(const spv_text text,
-                             const spv_opcode_table opcodeTable,
-                             const spv_operand_table operandTable,
-                             const spv_ext_inst_table extInstTable,
-                             spv_binary *pBinary, spv_diagnostic *pDiagnostic) {
+namespace {
+
+// Translates a given assembly language module into binary form.
+// If a diagnostic is generated, it is not yet marked as being
+// for a text-based input.
+spv_result_t spvTextToBinaryInternal(const spv_text text,
+                                     const spv_opcode_table opcodeTable,
+                                     const spv_operand_table operandTable,
+                                     const spv_ext_inst_table extInstTable,
+                                     spv_binary *pBinary,
+                                     spv_diagnostic *pDiagnostic) {
   spv_position_t position = {};
   spvCheck(!text->str || !text->length, DIAGNOSTIC << "Text stream is empty.";
            return SPV_ERROR_INVALID_TEXT);
@@ -742,6 +752,20 @@ spv_result_t spvTextToBinary(const spv_text text,
   return SPV_SUCCESS;
 }
 
+} // anonymous namespace
+
+spv_result_t spvTextToBinary(const spv_text text,
+                             const spv_opcode_table opcodeTable,
+                             const spv_operand_table operandTable,
+                             const spv_ext_inst_table extInstTable,
+                             spv_binary *pBinary, spv_diagnostic *pDiagnostic) {
+  spv_result_t result = spvTextToBinaryInternal(
+      text, opcodeTable, operandTable, extInstTable, pBinary, pDiagnostic);
+  if (pDiagnostic && *pDiagnostic) (*pDiagnostic)->isTextSource = true;
+
+  return result;
+}
+
 void spvTextDestroy(spv_text text) {
   spvCheck(!text, return );
   if (text->str) {
diff --git a/test/DiagnosticPrint.cpp b/test/DiagnosticPrint.cpp
index 9fe27928..f9fdf323 100644
--- a/test/DiagnosticPrint.cpp
+++ b/test/DiagnosticPrint.cpp
@@ -41,4 +41,7 @@ TEST(DiagnosticPrint, InvalidDiagnostic) {
   ASSERT_EQ(SPV_ERROR_INVALID_DIAGNOSTIC, spvDiagnosticPrint(nullptr));
 }
 
+// TODO(dneto): We should be able to redirect the diagnostic printing.
+// Once we do that, we can test diagnostic corner cases.
+
 }  // anonymous namespace