diff --git a/mlir/include/mlir/CAPI/Utils.h b/mlir/include/mlir/CAPI/Utils.h
index 022f09df6a5de1..07bf4167a96320 100644
--- a/mlir/include/mlir/CAPI/Utils.h
+++ b/mlir/include/mlir/CAPI/Utils.h
@@ -28,7 +28,8 @@ class CallbackOstream : public llvm::raw_ostream {
 public:
   CallbackOstream(std::function<void(const char *, intptr_t, void *)> callback,
                   void *opaqueData)
-      : callback(callback), opaqueData(opaqueData), pos(0u) {}
+      : raw_ostream(/*unbuffered=*/true), callback(callback),
+        opaqueData(opaqueData), pos(0u) {}
 
   void write_impl(const char *ptr, size_t size) override {
     callback(ptr, size, opaqueData);
diff --git a/mlir/lib/CAPI/IR/AffineExpr.cpp b/mlir/lib/CAPI/IR/AffineExpr.cpp
index 53954b78a81e2e..a4dd6cc4ebf57c 100644
--- a/mlir/lib/CAPI/IR/AffineExpr.cpp
+++ b/mlir/lib/CAPI/IR/AffineExpr.cpp
@@ -25,7 +25,6 @@ void mlirAffineExprPrint(MlirAffineExpr affineExpr, MlirStringCallback callback,
                          void *userData) {
   mlir::detail::CallbackOstream stream(callback, userData);
   unwrap(affineExpr).print(stream);
-  stream.flush();
 }
 
 void mlirAffineExprDump(MlirAffineExpr affineExpr) {
diff --git a/mlir/lib/CAPI/IR/AffineMap.cpp b/mlir/lib/CAPI/IR/AffineMap.cpp
index 6a87c269a42168..f8e78bcd46b20b 100644
--- a/mlir/lib/CAPI/IR/AffineMap.cpp
+++ b/mlir/lib/CAPI/IR/AffineMap.cpp
@@ -29,7 +29,6 @@ void mlirAffineMapPrint(MlirAffineMap affineMap, MlirStringCallback callback,
                         void *userData) {
   mlir::detail::CallbackOstream stream(callback, userData);
   unwrap(affineMap).print(stream);
-  stream.flush();
 }
 
 void mlirAffineMapDump(MlirAffineMap affineMap) { unwrap(affineMap).dump(); }
diff --git a/mlir/lib/CAPI/IR/Diagnostics.cpp b/mlir/lib/CAPI/IR/Diagnostics.cpp
index 9595446f9d5ab0..9cf422bb1b4f03 100644
--- a/mlir/lib/CAPI/IR/Diagnostics.cpp
+++ b/mlir/lib/CAPI/IR/Diagnostics.cpp
@@ -19,7 +19,6 @@ void mlirDiagnosticPrint(MlirDiagnostic diagnostic, MlirStringCallback callback,
                          void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(diagnostic).print(stream);
-  stream.flush();
 }
 
 MlirLocation mlirDiagnosticGetLocation(MlirDiagnostic diagnostic) {
diff --git a/mlir/lib/CAPI/IR/IR.cpp b/mlir/lib/CAPI/IR/IR.cpp
index 101e963159c97b..ad240fc9d75969 100644
--- a/mlir/lib/CAPI/IR/IR.cpp
+++ b/mlir/lib/CAPI/IR/IR.cpp
@@ -126,7 +126,6 @@ void mlirLocationPrint(MlirLocation location, MlirStringCallback callback,
                        void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(location).print(stream);
-  stream.flush();
 }
 
 /* ========================================================================== */
@@ -325,14 +324,12 @@ void mlirOperationPrint(MlirOperation op, MlirStringCallback callback,
                         void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(op)->print(stream);
-  stream.flush();
 }
 
 void mlirOperationPrintWithFlags(MlirOperation op, MlirOpPrintingFlags flags,
                                  MlirStringCallback callback, void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(op)->print(stream, *unwrap(flags));
-  stream.flush();
 }
 
 void mlirOperationDump(MlirOperation op) { return unwrap(op)->dump(); }
@@ -476,7 +473,6 @@ void mlirBlockPrint(MlirBlock block, MlirStringCallback callback,
                     void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(block)->print(stream);
-  stream.flush();
 }
 
 /* ========================================================================== */
@@ -523,7 +519,6 @@ void mlirValuePrint(MlirValue value, MlirStringCallback callback,
                     void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(value).print(stream);
-  stream.flush();
 }
 
 /* ========================================================================== */
@@ -543,7 +538,6 @@ int mlirTypeEqual(MlirType t1, MlirType t2) { return unwrap(t1) == unwrap(t2); }
 void mlirTypePrint(MlirType type, MlirStringCallback callback, void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(type).print(stream);
-  stream.flush();
 }
 
 void mlirTypeDump(MlirType type) { unwrap(type).dump(); }
@@ -572,7 +566,6 @@ void mlirAttributePrint(MlirAttribute attr, MlirStringCallback callback,
                         void *userData) {
   detail::CallbackOstream stream(callback, userData);
   unwrap(attr).print(stream);
-  stream.flush();
 }
 
 void mlirAttributeDump(MlirAttribute attr) { unwrap(attr).dump(); }