diff --git a/library/psa_its_file.c b/library/psa_its_file.c
index 2fbff20ef9..8dff7834de 100644
--- a/library/psa_its_file.c
+++ b/library/psa_its_file.c
@@ -51,6 +51,7 @@
 #define PSA_ITS_STORAGE_SUFFIX ".psa_its"
 #define PSA_ITS_STORAGE_FILENAME_LENGTH         \
     ( sizeof( PSA_ITS_STORAGE_PREFIX ) - 1 + /*prefix without terminating 0*/ \
+      16 + /*UID (64-bit number in hex)*/                               \
       16 + /*UID (64-bit number in hex)*/                               \
       sizeof( PSA_ITS_STORAGE_SUFFIX ) - 1 + /*suffix without terminating 0*/ \
       1 /*terminating null byte*/ )
diff --git a/tests/suites/test_suite_psa_its.function b/tests/suites/test_suite_psa_its.function
index 330846a02c..fb9ce07036 100644
--- a/tests/suites/test_suite_psa_its.function
+++ b/tests/suites/test_suite_psa_its.function
@@ -16,6 +16,7 @@
 #define PSA_ITS_STORAGE_SUFFIX ".psa_its"
 #define PSA_ITS_STORAGE_FILENAME_LENGTH         \
     ( sizeof( PSA_ITS_STORAGE_PREFIX ) - 1 + /*prefix without terminating 0*/ \
+      16 + /*UID (64-bit number in hex)*/                               \
       16 + /*UID (64-bit number in hex)*/                               \
       sizeof( PSA_ITS_STORAGE_SUFFIX ) - 1 + /*suffix without terminating 0*/ \
       1 /*terminating null byte*/ )