diff --git a/zap/src/main/java/org/parosproxy/paros/core/scanner/JsonParamParser.java b/zap/src/main/java/org/parosproxy/paros/core/scanner/JsonParamParser.java
index 1690348b68d..57d80f37a80 100644
--- a/zap/src/main/java/org/parosproxy/paros/core/scanner/JsonParamParser.java
+++ b/zap/src/main/java/org/parosproxy/paros/core/scanner/JsonParamParser.java
@@ -102,6 +102,7 @@ private void parseObject(int state, List<RPCParameter> list) {
         int endToken;
         int chr;
 
+        boolean primitive = false;
         while (!done) {
             switch (state) {
                 case STATE_INIT:
@@ -115,7 +116,7 @@ private void parseObject(int state, List<RPCParameter> list) {
                         state = STATE_READ_VALUE;
 
                     } else {
-                        // Lets see if its just a primitive string
+                        primitive = true;
                         sr.unreadLastCharacter();
                         state = STATE_READ_VALUE;
                     }
@@ -176,13 +177,13 @@ private void parseObject(int state, List<RPCParameter> list) {
                     break;
 
                 case STATE_READ_VALUE:
-                    if (field == null) {
+                    if (!primitive && field == null) {
                         // field is null when you have an untyped Object[], so we place
                         // the JsonArray on the @items field.
                         field = "@items";
                     }
 
-                    parseValue(field, list);
+                    parseValue(primitive, field, list);
                     state = STATE_READ_POST_VALUE;
                     break;
 
@@ -211,7 +212,7 @@ private static String getUnescapedValue(String value) {
         return StringEscapeUtils.unescapeJava(value);
     }
 
-    private void parseValue(String fieldName, List<RPCParameter> list) {
+    private void parseValue(boolean primitive, String fieldName, List<RPCParameter> list) {
         int chr = sr.read();
 
         // Check if the value is a string
@@ -233,7 +234,11 @@ private void parseValue(String fieldName, List<RPCParameter> list) {
             int beginToken = sr.getPosition();
             do {
                 chr = sr.read();
+
                 if (chr == -1) {
+                    if (primitive) {
+                        break;
+                    }
                     throw new IllegalArgumentException("Reached EOF while reading number");
                 }
 
@@ -244,7 +249,9 @@ private void parseValue(String fieldName, List<RPCParameter> list) {
                     || (chr == '+')
                     || (chr == '-'));
 
-            sr.unreadLastCharacter();
+            if (!primitive) {
+                sr.unreadLastCharacter();
+            }
             // Now we have the int object value
             // Put everything inside the parameter array
             int endToken = sr.getPosition();
@@ -298,7 +305,7 @@ private void parseArray(String fieldName, List<RPCParameter> list) {
         while (true) {
             sr.skipWhitespaceRead();
             sr.unreadLastCharacter();
-            parseValue(fieldName + "[" + (idx++) + "]", list);
+            parseValue(false, fieldName + "[" + (idx++) + "]", list);
 
             chr = sr.skipWhitespaceRead();
             if (chr == END_ARRAY) {
diff --git a/zap/src/test/java/org/parosproxy/paros/core/scanner/VariantJSONQueryUnitTest.java b/zap/src/test/java/org/parosproxy/paros/core/scanner/VariantJSONQueryUnitTest.java
index 53ce46ebf4f..13c0937ce48 100644
--- a/zap/src/test/java/org/parosproxy/paros/core/scanner/VariantJSONQueryUnitTest.java
+++ b/zap/src/test/java/org/parosproxy/paros/core/scanner/VariantJSONQueryUnitTest.java
@@ -419,6 +419,31 @@ void shouldReplacePrimitiveString() throws HttpMalformedHeaderException {
         assertThat(message.getRequestBody().toString(), is("\"injection\""));
     }
 
+    @Test
+    void shouldExtractPrimitiveNumbers() throws HttpMalformedHeaderException {
+        // Given
+        VariantJSONQuery variantJSONQuery = new VariantJSONQuery();
+        variantJSONQuery.setMessage(getMessageWithBody("12345"));
+        // When
+        List<NameValuePair> parameters = variantJSONQuery.getParamList();
+        // Then
+        assertThat(parameters.size(), is(equalTo(1)));
+        assertThat(parameters.get(0).getValue(), is("12345"));
+    }
+
+    @Test
+    void shouldReplacePrimitiveNumbers() throws HttpMalformedHeaderException {
+        // Given
+        VariantJSONQuery variantJSONQuery = new VariantJSONQuery();
+        HttpMessage message = getMessageWithBody("12345");
+        variantJSONQuery.setMessage(message);
+        // When
+        List<NameValuePair> parameters = variantJSONQuery.getParamList();
+        variantJSONQuery.setParameter(message, parameters.get(0), "", "injection");
+        // Then
+        assertThat(message.getRequestBody().toString(), is("\"injection\""));
+    }
+
     private static HttpMessage getMessageWithBody(String body) throws HttpMalformedHeaderException {
         return new HttpMessage(
                 new HttpRequestHeader(