diff --git a/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageHelperImpl.java b/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageHelperImpl.java
index 97a596674..384437b84 100644
--- a/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageHelperImpl.java
+++ b/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageHelperImpl.java
@@ -34,6 +34,7 @@ class ImageHelperImpl implements ImageHelper {
 	@Nullable
 	@Override
 	public String getExtensionFromMimeType(String mimeType) {
+		if ("image/webp".equals(mimeType)) return "webp";
 		MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
 		return mimeTypeMap.getExtensionFromMimeType(mimeType);
 	}
diff --git a/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageSizeCalculatorImpl.java b/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageSizeCalculatorImpl.java
index d0e6d6dae..0df8021da 100644
--- a/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageSizeCalculatorImpl.java
+++ b/briar-android/src/main/java/org/briarproject/briar/android/attachment/media/ImageSizeCalculatorImpl.java
@@ -21,6 +21,7 @@ import static androidx.exifinterface.media.ExifInterface.TAG_ORIENTATION;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @NotNullByDefault
 class ImageSizeCalculatorImpl implements ImageSizeCalculator {
@@ -61,6 +62,10 @@ class ImageSizeCalculatorImpl implements ImageSizeCalculator {
 				logException(LOG, WARNING, e);
 			}
 		}
+		if (!size.hasError() && isNullOrEmpty(size.getMimeType())) {
+			LOG.info("Could not determine content type, using supplied type");
+			size = new Size(size.getWidth(), size.getHeight(), contentType);
+		}
 		return size;
 	}