diff --git a/Cargo.toml b/Cargo.toml
index 26ef28e..aa9bbce 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "echtvar"
-version = "0.1.1"
+version = "0.1.2"
 edition = "2018"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
diff --git a/src/commands/annotate_cmd.rs b/src/commands/annotate_cmd.rs
index 6951033..f3698e7 100644
--- a/src/commands/annotate_cmd.rs
+++ b/src/commands/annotate_cmd.rs
@@ -129,6 +129,8 @@ pub fn annotate_main(
                 match v {
                     Value::Int(i) => match fld.ftype {
                         fields::FieldType::Categorical => {
+                            // categorical missing_value must be set to the index of the missing_string
+                            assert!(i >= 0, "can't have missing value for categorical!");
                             let val = [e.strings[fld.values_i][i as usize].as_bytes()];
                             record.push_info_string(fld.alias.as_bytes(), &val).expect(
                                 &format!("error adding string for {}", fld.alias).to_string(),
diff --git a/src/lib/echtvar.rs b/src/lib/echtvar.rs
index 8c919e5..efcae79 100644
--- a/src/lib/echtvar.rs
+++ b/src/lib/echtvar.rs
@@ -128,12 +128,9 @@ impl EchtVars {
             fc.read_to_string(&mut contents)
                 .expect("eror reading config.json");
             drop(fc);
-            let flds: Vec<fields::Field> = json5::from_str(&contents).unwrap();
-            eprintln!("fields: {:?}", flds);
-            for fld in flds {
-                let mut f = fld.clone();
-                f.values_i = result.fields.len();
-                result.fields.push(f);
+            let mut flds: Vec<fields::Field> = json5::from_str(&contents).unwrap();
+            for fld in flds.iter_mut() {
+                fld.values_i = result.fields.len();
                 if fld.ftype == fields::FieldType::Categorical {
                     // read in the strings for this field. replace ';' with ',' to handle the filter field.
                     let fname = format!("echtvar/strings/{}.txt", fld.alias);
@@ -144,13 +141,24 @@ impl EchtVars {
                     result
                         .strings
                         .push(BufReader::new(fh).lines().map(|l| l.unwrap().replace(";", ",")).collect());
+                    // update missing value to be the index of the missing_string
+                    let strings_len = result.strings[result.strings.len() - 1].len();
+                    fld.missing_value = result.strings[result.strings.len() - 1].iter().position(|s| s == &fld.missing_string).unwrap_or(strings_len) as i32;
+                    // if it wasn't in the list, add it.
+                    if fld.missing_value == strings_len as i32 {
+                        let rl = result.strings.len() - 1;
+                        result.strings[rl].push(fld.missing_string.clone());
+                    }
                 } else {
                     result.strings.push(Vec::new());
                 }
+                let f = fld.clone();
+                result.fields.push(f);
             }
             result.values.resize(result.fields.len(), vec![]);
             result.evalues.resize(result.fields.len(), Value::Int(0));
         }
+        eprintln!("fields: {:?}", result.fields);
         result
     }
 
@@ -363,6 +371,7 @@ impl EchtVars {
                     if fld.ftype == fields::FieldType::Integer
                         || fld.ftype == fields::FieldType::Categorical
                     {
+                        // for Categorical missing_value has been set to the index of missing_string
                         let val = fld.missing_value as i32;
                         self.evalues[fld.values_i] = Value::Int(val);
                         expr_values[fld.values_i] = val as f64
diff --git a/tests/check-string-for-issue8.py b/tests/check-string-for-issue8.py
new file mode 100644
index 0000000..c45ff3d
--- /dev/null
+++ b/tests/check-string-for-issue8.py
@@ -0,0 +1,9 @@
+import sys
+import gzip
+
+
+for line in gzip.open(sys.argv[1], 'rt'):
+    if line[0] == '#': continue
+
+    toks = line.strip().split("\t")
+    assert ";test_filter=OHNO" in toks[7]
diff --git a/tests/make-string-test-for-issue8.py b/tests/make-string-test-for-issue8.py
new file mode 100644
index 0000000..aecba09
--- /dev/null
+++ b/tests/make-string-test-for-issue8.py
@@ -0,0 +1,41 @@
+import itertools
+import random
+import sys
+
+
+#random.seed(42)
+
+fhdb = open("string-issue-8.db.vcf", "w")
+fhq = open("string-issue-8.query.vcf", "w")
+
+header = ("""##fileformat=VCFv4.2
+##FILTER=<ID=PASS,Description="All filters passed">
+##FILTER=<ID=FAIL,Description="All filters passed">
+##FILTER=<ID=OTHER,Description="All filters passed">
+##INFO=<ID=num,Number=1,Type=Integer,Description="random string value">
+##INFO=<ID=val,Number=.,Type=String,Description="random string value">
+##contig=<ID=chr1,length=248956422>
+##contig=<ID=1,length=248956422>
+#CHROM	POS	ID	REF	ALT	QUAL	FILTER	INFO""")
+
+FILTERS = ["PASS", "FAIL", "OTHER"]
+
+for fh in (fhdb, fhq):
+    print(header, file=fh)
+
+for switch in [1]:
+    switch = switch<<20
+
+    ref = "A"
+    alt = "C"
+    i = 12345
+
+    val = random.randint(0, 100)
+    flt = random.choice(FILTERS)
+    print(f"chr1\t{i}\t.\t{ref}\t{alt}\t1\t{flt}\tval=s{val};num=3", file=fhdb)
+    alt = "T"
+    print(f"chr1\t{i}\t.\t{ref}\t{alt}\t1\t{flt}\tval=s{val};num=3", file=fhq)
+
+
+with open("string-issue-8.json", "w") as fh:
+    fh.write("""[{"field": "FILTER", "alias":"test_filter", "missing_string": "OHNO"}]""")
diff --git a/tests/string.sh b/tests/string.sh
index bce97a6..afb2ded 100644
--- a/tests/string.sh
+++ b/tests/string.sh
@@ -16,3 +16,11 @@ python check-string.py string-anno.vcf.gz
 $echtvar anno -i "anno_num != 3" -e string.echtvar string.vcf string-anno.vcf.gz
 
 rm -f string.vcf  string.echtvar # string-anno.vcf.gz
+
+python make-string-test-for-issue8.py
+$echtvar encode issue8.echtvar string-issue-8.json string-issue-8.db.vcf
+$echtvar anno -e issue8.echtvar string-issue-8.query.vcf issue-8.output.vcf.gz
+python check-string-for-issue8.py issue-8.output.vcf.gz
+
+rm -r issue-8.output.vcf.gz issue8.echtvar string-issue-8.db.vcf string-issue-8.query.vcf string-issue-8.json
+