diff --git a/mkninja.sh b/mkninja.sh
index e1beb0f5..1422789b 100644
--- a/mkninja.sh
+++ b/mkninja.sh
@@ -488,7 +488,7 @@ buildlibrary libbackend.a \
     lib/utils.cc \
 
 FORMATS="\
-    40trackdrive \
+    40track_drive \
     acornadfs \
     acorndfs \
     aeslanier \
@@ -496,7 +496,7 @@ FORMATS="\
     amiga \
     ampro \
     apple2 \
-    apple2drive \
+    apple2_drive \
     appledos \
     atarist360 \
     atarist370 \
@@ -536,7 +536,7 @@ FORMATS="\
     northstar87 \
     prodos \
     rx50 \
-    shugartdrive \
+    shugart_drive \
     tids990 \
     vgi \
     victor9k_ds \
diff --git a/src/formats/40trackdrive.textpb b/src/formats/40track_drive.textpb
similarity index 100%
rename from src/formats/40trackdrive.textpb
rename to src/formats/40track_drive.textpb
diff --git a/src/formats/apple2drive.textpb b/src/formats/apple2_drive.textpb
similarity index 100%
rename from src/formats/apple2drive.textpb
rename to src/formats/apple2_drive.textpb
diff --git a/src/formats/shugartdrive.textpb b/src/formats/shugart_drive.textpb
similarity index 100%
rename from src/formats/shugartdrive.textpb
rename to src/formats/shugart_drive.textpb