diff --git a/src/gffread/config.vsh.yaml b/src/gffread/config.vsh.yaml
index e4ee2fd3..c7f3d551 100644
--- a/src/gffread/config.vsh.yaml
+++ b/src/gffread/config.vsh.yaml
@@ -50,7 +50,6 @@ argument_groups:
         alternatives: -o
         type: file
         direction: output
-        must_exist: false
         required: true
         description: |
           Write the output records into <outfile>.
diff --git a/src/samtools/samtools_flagstat/config.vsh.yaml b/src/samtools/samtools_flagstat/config.vsh.yaml
index 20a5e3cd..9b4dfbe1 100644
--- a/src/samtools/samtools_flagstat/config.vsh.yaml
+++ b/src/samtools/samtools_flagstat/config.vsh.yaml
@@ -28,6 +28,7 @@ argument_groups:
       description: |
         File containing samtools stats output.
       direction: output
+      required: true
       example: output.flagstat
    
 resources:
diff --git a/src/samtools/samtools_idxstats/config.vsh.yaml b/src/samtools/samtools_idxstats/config.vsh.yaml
index 781bd8be..d5e32077 100644
--- a/src/samtools/samtools_idxstats/config.vsh.yaml
+++ b/src/samtools/samtools_idxstats/config.vsh.yaml
@@ -29,7 +29,7 @@ argument_groups:
         description: |
           File containing samtools stats output in tab-delimited format.
         required: true
-        must_exist: false
+        direction: output
         example: output.idxstats
    
 resources: