diff --git a/src/lib/Hydra/Plugin/RunCommand.pm b/src/lib/Hydra/Plugin/RunCommand.pm
index 8d3cf35a..8998fc39 100644
--- a/src/lib/Hydra/Plugin/RunCommand.pm
+++ b/src/lib/Hydra/Plugin/RunCommand.pm
@@ -41,6 +41,32 @@ sub isBuildEligibleForDynamicRunCommand {
     my ($build) = @_;
 
     if ($build->get_column("job") =~ "^runCommandHook\..+") {
+        my $out = $build->buildoutputs->find({name => "out"});
+        if (!defined $out) {
+            warn "DynamicRunCommand hook on " . $build->job . " (" . $build->id . ") rejected: no output named 'out'.";
+            return 0;
+        }
+
+        my $path = $out->path;
+        if (-l $path) {
+            $path = readlink($path);
+        }
+
+        if (! -e $path) {
+            warn "DynamicRunCommand hook on " . $build->job . " (" . $build->id . ") rejected: The 'out' output doesn't exist locally. This is a bug.";
+            return 0;
+        }
+
+        if (! -x $path) {
+            warn "DynamicRunCommand hook on " . $build->job . " (" . $build->id . ") rejected: The 'out' output is not executable.";
+            return 0;
+        }
+
+        if (! -f $path) {
+            warn "DynamicRunCommand hook on " . $build->job . " (" . $build->id . ") rejected: The 'out' output is not a regular file or symlink.";
+            return 0;
+        }
+
         return 1;
     }
 
@@ -109,9 +135,7 @@ sub fanoutToCommands {
         # missing test cases:
         #
         # 1. is it enabled on the jobset?
-        # 2. what if the result is a directory?
-        # 3. what if the job doens't have an out?
-        # 4. what if the build failed?
+        # 2. what if the build failed?
         if (isBuildEligibleForDynamicRunCommand($build)) {
             my $job = $build->get_column('job');
             my $out = $build->buildoutputs->find({name => "out"});
diff --git a/t/Hydra/Plugin/RunCommand/fanout.t b/t/Hydra/Plugin/RunCommand/fanout.t
index d9f67f14..41236456 100644
--- a/t/Hydra/Plugin/RunCommand/fanout.t
+++ b/t/Hydra/Plugin/RunCommand/fanout.t
@@ -93,36 +93,72 @@ subtest "fanoutToCommandsWithDynamicRunCommandSupport" => sub {
 };
 
 subtest "isBuildEligibleForDynamicRunCommand" => sub {
-    my $build = Hydra::Schema::Result::Builds->new({
-        "job" => "foo bar baz"
-    });
+    subtest "Non-matches based on name alone ..." => sub {
+        my $build = $builds->{"foo-bar-baz"};
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($build),
+            0,
+            "The job name does not match"
+        );
 
-    is(
-        Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($build),
-        0,
-        "The job name does not match"
-    );
+        $build->set_column("job", "runCommandHook");
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($build),
+            0,
+            "The job name does not match"
+        );
 
-    $build->set_column("job", "runCommandHook");
-    is(
-        Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($build),
-        0,
-        "The job name does not match"
-    );
+        $build->set_column("job", "runCommandHook.");
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($build),
+            0,
+            "The job name does not match"
+        );
+    };
 
-    $build->set_column("job", "runCommandHook.");
-    is(
-        Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($build),
-        0,
-        "The job name does not match"
-    );
+    subtest "On outputs ..." => sub {
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($builds->{"runCommandHook.example"}),
+            1,
+            "out is an executable file"
+        );
 
-    $build->set_column("job", "runCommandHook.a");
-    is(
-        Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($build),
-        1,
-        "The job name does match"
-    );
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($builds->{"runCommandHook.symlink"}),
+            1,
+            "out is a symlink to an executable file"
+        );
+
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($builds->{"runCommandHook.no-out"}),
+            0,
+            "No output named out"
+        );
+
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($builds->{"runCommandHook.out-is-directory"}),
+            0,
+            "out is a directory"
+        );
+
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($builds->{"runCommandHook.out-is-not-executable-file"}),
+            0,
+            "out is a file which is not not executable"
+        );
+
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($builds->{"runCommandHook.symlink-non-executable"}),
+            0,
+            "out is a symlink to a non-executable file"
+        );
+
+        is(
+            Hydra::Plugin::RunCommand::isBuildEligibleForDynamicRunCommand($builds->{"runCommandHook.symlink-directory"}),
+            0,
+            "out is a symlink to a directory"
+        );
+    };
 };
 
 
diff --git a/t/jobs/runcommand-dynamic.nix b/t/jobs/runcommand-dynamic.nix
index cf231f8f..c0b005b7 100644
--- a/t/jobs/runcommand-dynamic.nix
+++ b/t/jobs/runcommand-dynamic.nix
@@ -1,27 +1,130 @@
 with import ./config.nix;
-{
-  runCommandHook.example = mkDerivation
-    {
-      name = "my-build-product";
-      builder = "/bin/sh";
-      outputs = [ "out" "bin" ];
-      args = [
-        (
-          builtins.toFile "builder.sh" ''
-            #! /bin/sh
+rec {
+  foo-bar-baz = mkDerivation {
+    name = "foo-bar-baz";
+    builder = "/bin/sh";
+    outputs = [ "out" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
 
-            echo "$PATH"
+          touch $out
+        ''
+      )
+    ];
+  };
 
-            mkdir $bin
-            echo "foo" > $bin/bar
+  runCommandHook.example = mkDerivation {
+    name = "my-build-product";
+    builder = "/bin/sh";
+    outputs = [ "out" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
 
-            metrics=$out/nix-support/hydra-metrics
-            mkdir -p "$(dirname "$metrics")"
-            echo "lineCoverage 18 %" >> "$metrics"
-            echo "maxResident 27 KiB" >> "$metrics"
-          ''
-        )
-      ];
-    };
+          touch $out
+          chmod +x $out
+          # ... dunno ...
+        ''
+      )
+    ];
+  };
+
+  runCommandHook.symlink = mkDerivation {
+    name = "symlink-out";
+    builder = "/bin/sh";
+    outputs = [ "out" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
+
+          ln -s $1 $out
+        ''
+      )
+
+      runCommandHook.example
+    ];
+  };
+
+  runCommandHook.no-out = mkDerivation {
+    name = "no-out";
+    builder = "/bin/sh";
+    outputs = [ "bin" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
+          mkdir $bin
+        ''
+      )
+    ];
+  };
+
+  runCommandHook.out-is-directory = mkDerivation {
+    name = "out-is-directory";
+    builder = "/bin/sh";
+    outputs = [ "out" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
+
+          mkdir $out
+        ''
+      )
+    ];
+  };
+
+  runCommandHook.out-is-not-executable-file = mkDerivation {
+    name = "out-is-directory";
+    builder = "/bin/sh";
+    outputs = [ "out" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
+
+          touch $out
+        ''
+      )
+    ];
+  };
+
+  runCommandHook.symlink-non-executable = mkDerivation {
+    name = "symlink-out";
+    builder = "/bin/sh";
+    outputs = [ "out" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
+
+          ln -s $1 $out
+        ''
+      )
+
+      runCommandHook.out-is-not-executable-file
+    ];
+  };
+
+  runCommandHook.symlink-directory = mkDerivation {
+    name = "symlink-directory";
+    builder = "/bin/sh";
+    outputs = [ "out" ];
+    args = [
+      (
+        builtins.toFile "builder.sh" ''
+          #! /bin/sh
+
+          ln -s $1 $out
+        ''
+      )
+
+      runCommandHook.out-is-directory
+    ];
+  };
 
 }