diff --git a/packages/build/src/error/parse/normalize.js b/packages/build/src/error/parse/normalize.js
new file mode 100644
index 0000000000..1c0a88e499
--- /dev/null
+++ b/packages/build/src/error/parse/normalize.js
@@ -0,0 +1,21 @@
+// Ensure error is an `Error` instance
+const normalizeError = function(error) {
+  if (error instanceof Array) {
+    return normalizeArray(error)
+  }
+
+  if (error instanceof Error && typeof error.message === 'string' && typeof error.stack === 'string') {
+    return error
+  }
+
+  return new Error(String(error))
+}
+
+// Some libraries throw arrays of Errors
+const normalizeArray = function(errorArray) {
+  const [error, ...errors] = errorArray.map(normalizeError)
+  error.errors = errors
+  return error
+}
+
+module.exports = { normalizeError }
diff --git a/packages/build/src/error/parse/parse.js b/packages/build/src/error/parse/parse.js
index e70d5a11fd..8a8827064a 100644
--- a/packages/build/src/error/parse/parse.js
+++ b/packages/build/src/error/parse/parse.js
@@ -2,6 +2,7 @@ const { getErrorInfo } = require('../info')
 const { getTypeInfo } = require('../type')
 
 const { getLocationInfo } = require('./location')
+const { normalizeError } = require('./normalize')
 const { getPluginInfo } = require('./plugin')
 const { getErrorProps } = require('./properties')
 const { getStackInfo } = require('./stack')
@@ -61,14 +62,6 @@ const parseErrorInfo = function(error) {
   }
 }
 
-const normalizeError = function(error) {
-  if (error instanceof Error && typeof error.message === 'string' && typeof error.stack === 'string') {
-    return error
-  }
-
-  return new Error(String(error))
-}
-
 // Retrieve title to print in logs
 const getTitle = function(title, errorInfo) {
   if (typeof title !== 'function') {
diff --git a/packages/build/src/plugins/child/error.js b/packages/build/src/plugins/child/error.js
index f48f8778f6..6d0602fb99 100644
--- a/packages/build/src/plugins/child/error.js
+++ b/packages/build/src/plugins/child/error.js
@@ -3,11 +3,13 @@ const logProcessErrors = require('log-process-errors')
 
 const { errorToJson } = require('../../error/build')
 const { isBuildError } = require('../../error/info')
+const { normalizeError } = require('../../error/parse/normalize')
 const { sendEventToParent } = require('../ipc')
 
 // Handle any top-level error and communicate it back to parent
 const handleError = async function(error) {
-  const errorPayload = errorToJson(error, { type: 'pluginInternal' })
+  const errorA = normalizeError(error)
+  const errorPayload = errorToJson(errorA, { type: 'pluginInternal' })
   await sendEventToParent('error', errorPayload)
 }
 
diff --git a/packages/build/tests/error/fixtures/exception_array/manifest.yml b/packages/build/tests/error/fixtures/exception_array/manifest.yml
new file mode 100644
index 0000000000..a3512f0259
--- /dev/null
+++ b/packages/build/tests/error/fixtures/exception_array/manifest.yml
@@ -0,0 +1,2 @@
+name: test
+inputs: []
diff --git a/packages/build/tests/error/fixtures/exception_array/netlify.toml b/packages/build/tests/error/fixtures/exception_array/netlify.toml
new file mode 100644
index 0000000000..81b0ce8bb1
--- /dev/null
+++ b/packages/build/tests/error/fixtures/exception_array/netlify.toml
@@ -0,0 +1,2 @@
+[[plugins]]
+package = "./plugin"
diff --git a/packages/build/tests/error/fixtures/exception_array/plugin.js b/packages/build/tests/error/fixtures/exception_array/plugin.js
new file mode 100644
index 0000000000..96f23893a6
--- /dev/null
+++ b/packages/build/tests/error/fixtures/exception_array/plugin.js
@@ -0,0 +1,5 @@
+module.exports = {
+  async onPreBuild() {
+    throw [new Error('test'), new Error('testTwo')]
+  },
+}
diff --git a/packages/build/tests/error/fixtures/exception_string/manifest.yml b/packages/build/tests/error/fixtures/exception_string/manifest.yml
new file mode 100644
index 0000000000..a3512f0259
--- /dev/null
+++ b/packages/build/tests/error/fixtures/exception_string/manifest.yml
@@ -0,0 +1,2 @@
+name: test
+inputs: []
diff --git a/packages/build/tests/error/fixtures/exception_string/netlify.toml b/packages/build/tests/error/fixtures/exception_string/netlify.toml
new file mode 100644
index 0000000000..81b0ce8bb1
--- /dev/null
+++ b/packages/build/tests/error/fixtures/exception_string/netlify.toml
@@ -0,0 +1,2 @@
+[[plugins]]
+package = "./plugin"
diff --git a/packages/build/tests/error/fixtures/exception_string/plugin.js b/packages/build/tests/error/fixtures/exception_string/plugin.js
new file mode 100644
index 0000000000..b0803cd819
--- /dev/null
+++ b/packages/build/tests/error/fixtures/exception_string/plugin.js
@@ -0,0 +1,5 @@
+module.exports = {
+  async onPreBuild() {
+    throw 'test'
+  },
+}
diff --git a/packages/build/tests/error/snapshots/tests.js.md b/packages/build/tests/error/snapshots/tests.js.md
index 9780cf5b24..4942482c41 100644
--- a/packages/build/tests/error/snapshots/tests.js.md
+++ b/packages/build/tests/error/snapshots/tests.js.md
@@ -3415,6 +3415,133 @@ Generated by [AVA](https://ava.li).
 
 ## exception
 
+> Snapshot 1
+
+    `␊
+    ┌─────────────────────────────┐␊
+    │        Netlify Build        │␊
+    └─────────────────────────────┘␊
+    ␊
+    > Version␊
+      @netlify/build 1.0.0␊
+    ␊
+    > Flags␊
+      debug: true␊
+      repositoryRoot: /file/path␊
+    ␊
+    > Current directory␊
+      /file/path␊
+    ␊
+    > Config file␊
+      /file/path␊
+    ␊
+    > Resolved config␊
+      plugins:␊
+        - inputs: {}␊
+          origin: config␊
+          package: /file/path␊
+    ␊
+    > Context␊
+      production␊
+    ␊
+    > Loading plugins␊
+       - /file/path from netlify.toml␊
+    ␊
+    ┌─────────────────────────────────────┐␊
+    │ 1. onPreBuild command from /file/path │␊
+    └─────────────────────────────────────┘␊
+    ␊
+    ␊
+    ┌──────────────────────────────────┐␊
+    │ Plugin "/file/path" internal error │␊
+    └──────────────────────────────────┘␊
+    ␊
+      Error message␊
+      Error: test␊
+    ␊
+      Plugin details␊
+      Package:        /file/path␊
+      Version:        1.0.0␊
+      Repository:     git+https://github.com/netlify/build.git␊
+      Report issues:  https://github.com/netlify/build/issues␊
+    ␊
+      Error location␊
+      In "onPreBuild" event in "/file/path" from netlify.toml␊
+    STACK TRACE␊
+    ␊
+      Resolved config␊
+      plugins:␊
+        - inputs: {}␊
+          origin: config␊
+          package: /file/path`
+
+## exception that are arrays
+
+> Snapshot 1
+
+    `␊
+    ┌─────────────────────────────┐␊
+    │        Netlify Build        │␊
+    └─────────────────────────────┘␊
+    ␊
+    > Version␊
+      @netlify/build 1.0.0␊
+    ␊
+    > Flags␊
+      debug: true␊
+      repositoryRoot: /file/path␊
+    ␊
+    > Current directory␊
+      /file/path␊
+    ␊
+    > Config file␊
+      /file/path␊
+    ␊
+    > Resolved config␊
+      plugins:␊
+        - inputs: {}␊
+          origin: config␊
+          package: /file/path␊
+    ␊
+    > Context␊
+      production␊
+    ␊
+    > Loading plugins␊
+       - /file/path from netlify.toml␊
+    ␊
+    ┌─────────────────────────────────────┐␊
+    │ 1. onPreBuild command from /file/path │␊
+    └─────────────────────────────────────┘␊
+    ␊
+    ␊
+    ┌──────────────────────────────────┐␊
+    │ Plugin "/file/path" internal error │␊
+    └──────────────────────────────────┘␊
+    ␊
+      Error message␊
+      Error: test␊
+    ␊
+      Plugin details␊
+      Package:        /file/path␊
+      Version:        1.0.0␊
+      Repository:     git+https://github.com/netlify/build.git␊
+      Report issues:  https://github.com/netlify/build/issues␊
+    ␊
+      Error location␊
+      In "onPreBuild" event in "/file/path" from netlify.toml␊
+    STACK TRACE␊
+    ␊
+      Error properties␊
+      { errors: [ {} ] }␊
+    ␊
+      Resolved config␊
+      plugins:␊
+        - inputs: {}␊
+          origin: config␊
+          package: /file/path`
+
+## exception that are strings
+
 > Snapshot 1
 
     `␊
diff --git a/packages/build/tests/error/snapshots/tests.js.snap b/packages/build/tests/error/snapshots/tests.js.snap
index e84b0c8ace..c21e4fa9d0 100644
Binary files a/packages/build/tests/error/snapshots/tests.js.snap and b/packages/build/tests/error/snapshots/tests.js.snap differ
diff --git a/packages/build/tests/error/tests.js b/packages/build/tests/error/tests.js
index c045a7917b..b6e63775c1 100644
--- a/packages/build/tests/error/tests.js
+++ b/packages/build/tests/error/tests.js
@@ -86,6 +86,14 @@ test('exception with circular references', async t => {
   await runFixture(t, 'exception_circular')
 })
 
+test('exception that are strings', async t => {
+  await runFixture(t, 'exception_string')
+})
+
+test('exception that are arrays', async t => {
+  await runFixture(t, 'exception_array')
+})
+
 test('Clean stack traces of build.command', async t => {
   const { returnValue } = await runFixture(t, 'build_command', { snapshot: false, normalize: false })
   const count = getStackLinesCount(returnValue)