diff --git a/backends/aiger/aiger.cc b/backends/aiger/aiger.cc
index 0798fb35d..3e8b14dee 100644
--- a/backends/aiger/aiger.cc
+++ b/backends/aiger/aiger.cc
@@ -777,7 +777,7 @@ struct AigerBackend : public Backend {
 			}
 			break;
 		}
-		extra_args(f, filename, args, argidx);
+		extra_args(f, filename, args, argidx, !ascii_mode);
 
 		Module *top_module = design->top_module();
 
diff --git a/backends/aiger/xaiger.cc b/backends/aiger/xaiger.cc
index fa6ba0aca..87ba0aedf 100644
--- a/backends/aiger/xaiger.cc
+++ b/backends/aiger/xaiger.cc
@@ -856,7 +856,7 @@ struct XAigerBackend : public Backend {
 			}
 			break;
 		}
-		extra_args(f, filename, args, argidx);
+		extra_args(f, filename, args, argidx, !ascii_mode);
 
 		Module *top_module = design->top_module();
 
diff --git a/backends/protobuf/protobuf.cc b/backends/protobuf/protobuf.cc
index fff110bb0..671686173 100644
--- a/backends/protobuf/protobuf.cc
+++ b/backends/protobuf/protobuf.cc
@@ -266,7 +266,7 @@ struct ProtobufBackend : public Backend {
 			}
 			break;
 		}
-		extra_args(f, filename, args, argidx);
+		extra_args(f, filename, args, argidx, !text_mode);
 
 		log_header(design, "Executing Protobuf backend.\n");
 
@@ -338,7 +338,7 @@ struct ProtobufPass : public Pass {
 		if (!filename.empty()) {
 			rewrite_filename(filename);
 			std::ofstream *ff = new std::ofstream;
-			ff->open(filename.c_str(), std::ofstream::trunc);
+			ff->open(filename.c_str(), text_mode ? std::ofstream::trunc : (std::ofstream::trunc | std::ofstream::binary));
 			if (ff->fail()) {
 				delete ff;
 				log_error("Can't open file `%s' for writing: %s\n", filename.c_str(), strerror(errno));
diff --git a/kernel/register.cc b/kernel/register.cc
index 8131fa279..3033ee710 100644
--- a/kernel/register.cc
+++ b/kernel/register.cc
@@ -612,7 +612,7 @@ void Backend::execute(std::vector<std::string> args, RTLIL::Design *design)
 		delete f;
 }
 
-void Backend::extra_args(std::ostream *&f, std::string &filename, std::vector<std::string> args, size_t argidx)
+void Backend::extra_args(std::ostream *&f, std::string &filename, std::vector<std::string> args, size_t argidx, bool bin_output)
 {
 	bool called_with_fp = f != NULL;
 
@@ -647,7 +647,7 @@ void Backend::extra_args(std::ostream *&f, std::string &filename, std::vector<st
 #endif
 		} else {
 			std::ofstream *ff = new std::ofstream;
-			ff->open(filename.c_str(), std::ofstream::trunc);
+			ff->open(filename.c_str(), bin_output ? (std::ofstream::trunc | std::ofstream::binary) : std::ofstream::trunc);
 			yosys_output_files.insert(filename);
 			if (ff->fail()) {
 				delete ff;
diff --git a/kernel/register.h b/kernel/register.h
index c74029823..be836013f 100644
--- a/kernel/register.h
+++ b/kernel/register.h
@@ -109,7 +109,7 @@ struct Backend : Pass
 	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE YS_FINAL;
 	virtual void execute(std::ostream *&f, std::string filename,  std::vector<std::string> args, RTLIL::Design *design) = 0;
 
-	void extra_args(std::ostream *&f, std::string &filename, std::vector<std::string> args, size_t argidx);
+	void extra_args(std::ostream *&f, std::string &filename, std::vector<std::string> args, size_t argidx, bool bin_output = false);
 
 	static void backend_call(RTLIL::Design *design, std::ostream *f, std::string filename, std::string command);
 	static void backend_call(RTLIL::Design *design, std::ostream *f, std::string filename, std::vector<std::string> args);