diff --git a/src/patch/register.rs b/src/patch/register.rs
index fc40abc9..c152b3bd 100644
--- a/src/patch/register.rs
+++ b/src/patch/register.rs
@@ -3,6 +3,7 @@ use svd_parser::svd::{
     Access, BitRange, DimElement, EnumeratedValues, Field, FieldInfo, ModifiedWriteValues,
     ReadAction, Register, RegisterInfo, Usage, WriteConstraint, WriteConstraintRange,
 };
+use svd_rs::ValidateLevel;
 use yaml_rust::{yaml::Hash, Yaml};
 
 use super::iterators::{MatchIter, Matched};
@@ -720,6 +721,7 @@ impl RegisterExt for Register {
                 min: fmod[0].i64()? as u64,
                 max: fmod[1].i64()? as u64,
             }));
+            ftag.validate(ValidateLevel::Weak)?;
             set_any = true;
         }
         if !set_any {