diff --git a/lib/dns/resource.js b/lib/dns/resource.js
index dbf3a78fd3..c4afd15dd8 100644
--- a/lib/dns/resource.js
+++ b/lib/dns/resource.js
@@ -349,11 +349,11 @@ class Resource extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(Array.isArray(json.records));
+    assert(json && typeof json === 'object', 'Invalid json.');
+    assert(Array.isArray(json.records), 'Invalid records.');
 
     for (const item of json.records) {
-      assert(item && typeof item === 'object');
+      assert(item && typeof item === 'object', 'Invalid record.');
 
       const RD = stringToClass(item.type);
 
@@ -437,13 +437,17 @@ class DS extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'DS');
-    assert((json.keyTag & 0xffff) === json.keyTag);
-    assert((json.algorithm & 0xff) === json.algorithm);
-    assert((json.digestType & 0xff) === json.digestType);
-    assert(typeof json.digest === 'string');
-    assert((json.digest.length >>> 1) <= 255);
+    assert(json && typeof json === 'object', 'Invalid json in DS record.');
+    assert(json.type === 'DS', 'Invalid type in DS record.');
+    assert((json.keyTag & 0xffff) === json.keyTag,
+      'Invalid keyTag in DS record.');
+    assert((json.algorithm & 0xff) === json.algorithm,
+      'Invalid algorithm in DS record.');
+    assert((json.digestType & 0xff) === json.digestType,
+      'Invalid digestType in DS record.');
+    assert(typeof json.digest === 'string', 'Invalid digest in DS record.');
+    assert((json.digest.length >>> 1) <= 255,
+      'Invalid digest length in DS record.');
 
     this.keyTag = json.keyTag;
     this.algorithm = json.algorithm;
@@ -495,9 +499,9 @@ class NS extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'NS');
-    assert(isName(json.ns));
+    assert(json && typeof json === 'object', 'Invalid json in NS record.');
+    assert(json.type === 'NS', 'Invalid type in NS record.');
+    assert(isName(json.ns), 'Invalid ns in NS record.');
 
     this.ns = json.ns;
 
@@ -554,10 +558,10 @@ class GLUE4 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'GLUE4');
-    assert(isName(json.ns));
-    assert(IP.isIPv4String(json.address));
+    assert(json && typeof json === 'object', 'Invalid json in GLUE4 record.');
+    assert(json.type === 'GLUE4', 'Invalid type in GLUE4 record.');
+    assert(isName(json.ns), 'Invalid ns in GLUE4 record.');
+    assert(IP.isIPv4String(json.address), 'Invalid address in GLUE4 record.');
 
     this.ns = json.ns;
     this.address = IP.normalize(json.address);
@@ -615,10 +619,10 @@ class GLUE6 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'GLUE6');
-    assert(isName(json.ns));
-    assert(IP.isIPv6String(json.address));
+    assert(json && typeof json === 'object', 'Invalid JSON in GLUE6 record.');
+    assert(json.type === 'GLUE6', 'Invalid type in GLUE6 record.');
+    assert(isName(json.ns), 'Invalid ns in GLUE6 record.');
+    assert(IP.isIPv6String(json.address), 'Invalid address in GLUE6 record.');
 
     this.ns = json.ns;
     this.address = IP.normalize(json.address);
@@ -677,9 +681,9 @@ class SYNTH4 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'SYNTH4');
-    assert(IP.isIPv4String(json.address));
+    assert(json && typeof json === 'object', 'Invalid json in SYNTH4 record.');
+    assert(json.type === 'SYNTH4', 'Invalid type in SYNTH4 record.');
+    assert(IP.isIPv4String(json.address), 'Invalid address in SYNTH4 record.');
 
     this.address = IP.normalize(json.address);
 
@@ -737,9 +741,9 @@ class SYNTH6 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'SYNTH6');
-    assert(IP.isIPv6String(json.address));
+    assert(json && typeof json === 'object', 'Invalid json in SYNTH6 record.');
+    assert(json.type === 'SYNTH6', 'Invalid type in SYNTH6 record.');
+    assert(IP.isIPv6String(json.address), 'Invalid address in SYNTH6 record.');
 
     this.address = IP.normalize(json.address);
 
@@ -812,13 +816,13 @@ class TXT extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'TXT');
-    assert(Array.isArray(json.txt));
+    assert(json && typeof json === 'object', 'Invalid json in TXT record.');
+    assert(json.type === 'TXT', 'Invalid type in TXT record.');
+    assert(Array.isArray(json.txt), 'Invalid txt in TXT record.');
 
     for (const txt of json.txt) {
-      assert(typeof txt === 'string');
-      assert(txt.length <= 255);
+      assert(typeof txt === 'string', 'Invalid txt entry in TXT record.');
+      assert(txt.length <= 255, 'Invalid txt entry length in TXT record.');
 
       this.txt.push(txt);
     }