diff --git a/include/libcamera/internal/software_isp/software_isp.h b/include/libcamera/internal/software_isp/software_isp.h
index af0dcc24..f2344355 100644
--- a/include/libcamera/internal/software_isp/software_isp.h
+++ b/include/libcamera/internal/software_isp/software_isp.h
@@ -101,6 +101,7 @@ private:
 
 	std::unique_ptr<ipa::soft::IPAProxySoft> ipa_;
 	bool running_;
+	std::deque<FrameBuffer *> queuedOutputBuffers_;
 };
 
 } /* namespace libcamera */
diff --git a/src/libcamera/software_isp/software_isp.cpp b/src/libcamera/software_isp/software_isp.cpp
index 1a39f4d8..4339e547 100644
--- a/src/libcamera/software_isp/software_isp.cpp
+++ b/src/libcamera/software_isp/software_isp.cpp
@@ -17,6 +17,7 @@
 #include <libcamera/formats.h>
 #include <libcamera/stream.h>
 
+#include "libcamera/internal/framebuffer.h"
 #include "libcamera/internal/ipa_manager.h"
 #include "libcamera/internal/software_isp/debayer_params.h"
 
@@ -300,8 +301,11 @@ int SoftwareIsp::queueBuffers(uint32_t frame, FrameBuffer *input,
 			return -EINVAL;
 	}
 
-	for (auto iter = outputs.begin(); iter != outputs.end(); iter++)
-		process(frame, input, iter->second);
+	for (auto iter = outputs.begin(); iter != outputs.end(); iter++) {
+		FrameBuffer *const buffer = iter->second;
+		queuedOutputBuffers_.push_back(buffer);
+		process(frame, input, buffer);
+	}
 
 	return 0;
 }
@@ -331,6 +335,13 @@ void SoftwareIsp::stop()
 
 	running_ = false;
 	ipa_->stop();
+
+	for (auto buffer : queuedOutputBuffers_) {
+		FrameMetadata &metadata = buffer->_d()->metadata();
+		metadata.status = FrameMetadata::FrameCancelled;
+		outputBufferReady.emit(buffer);
+	}
+	queuedOutputBuffers_.clear();
 }
 
 /**
@@ -369,7 +380,12 @@ void SoftwareIsp::inputReady(FrameBuffer *input)
 
 void SoftwareIsp::outputReady(FrameBuffer *output)
 {
-	outputBufferReady.emit(output);
+	if (running_) {
+		queuedOutputBuffers_.erase(find(queuedOutputBuffers_.begin(),
+						queuedOutputBuffers_.end(),
+						output));
+		outputBufferReady.emit(output);
+	}
 }
 
 } /* namespace libcamera */