diff --git a/src/lib/bootloader/cpu_mitigations.rb b/src/lib/bootloader/cpu_mitigations.rb
index 05f1aaf69..dbb375faa 100644
--- a/src/lib/bootloader/cpu_mitigations.rb
+++ b/src/lib/bootloader/cpu_mitigations.rb
@@ -42,7 +42,11 @@ def self.from_kernel_params(kernel_params)
       log.info "mitigation param #{param.inspect}"
       param = nil if param == false
       reverse_mapping = KERNEL_MAPPING.invert
-      raise "Unknown mitigations value #{param.inspect}" if !reverse_mapping.key?(param)
+
+      if !reverse_mapping.key?(param)
+        raise "Unknown mitigations value #{param.inspect} in the kernel command line, " \
+          "supported values are: #{KERNEL_MAPPING.values.compact.map(&:inspect).join(", ")}."
+      end
 
       new(reverse_mapping[param])
     end