diff --git a/.changeset/popular-bugs-draw.md b/.changeset/popular-bugs-draw.md
new file mode 100644
index 0000000000..4121082794
--- /dev/null
+++ b/.changeset/popular-bugs-draw.md
@@ -0,0 +1,5 @@
+---
+"supi": patch
+---
+
+When updating specs in the lockfile, read the specs from the manifest in the right order: optionalDependencies > dependencies > devDependencies.
diff --git a/packages/supi/src/getSpecFromPackageManifest.ts b/packages/supi/src/getSpecFromPackageManifest.ts
index ec14a6dced..cbf96811f8 100644
--- a/packages/supi/src/getSpecFromPackageManifest.ts
+++ b/packages/supi/src/getSpecFromPackageManifest.ts
@@ -4,8 +4,8 @@ export default (
   manifest: Pick<ProjectManifest, 'devDependencies' | 'dependencies' | 'optionalDependencies'>,
   depName: string
 ) => {
-  return manifest.dependencies?.[depName] ??
+  return manifest.optionalDependencies?.[depName] ??
+    manifest.dependencies?.[depName] ??
     manifest.devDependencies?.[depName] ??
-    manifest.optionalDependencies?.[depName] ??
     ''
 }
diff --git a/packages/supi/src/install/getWantedDependencies.ts b/packages/supi/src/install/getWantedDependencies.ts
index 264f3070e5..ff3cabac18 100644
--- a/packages/supi/src/install/getWantedDependencies.ts
+++ b/packages/supi/src/install/getWantedDependencies.ts
@@ -31,6 +31,7 @@ export default function getWantedDependencies (
       optionalDependencies: true,
     })
   return getWantedDependenciesFromGivenSet(depsToInstall, {
+    dependencies: pkg.dependencies ?? {},
     devDependencies: pkg.devDependencies ?? {},
     optionalDependencies: pkg.optionalDependencies ?? {},
     updatePref: opts?.updateWorkspaceDependencies === true
@@ -46,6 +47,7 @@ function updateWorkspacePref (pref: string) {
 function getWantedDependenciesFromGivenSet (
   deps: Dependencies,
   opts: {
+    dependencies: Dependencies
     devDependencies: Dependencies
     optionalDependencies: Dependencies
     updatePref: (pref: string) => string
@@ -54,10 +56,14 @@ function getWantedDependenciesFromGivenSet (
   if (!deps) return []
   return Object.keys(deps).map((alias) => {
     const pref = opts.updatePref(deps[alias])
+    let depType
+    if (opts.optionalDependencies[alias] != null) depType = 'optional'
+    else if (opts.dependencies[alias] != null) depType = 'prod'
+    else if (opts.devDependencies[alias] != null) depType = 'dev'
     return {
       alias,
-      dev: !!opts.devDependencies[alias],
-      optional: !!opts.optionalDependencies[alias],
+      dev: depType === 'dev',
+      optional: depType === 'optional',
       pinnedVersion: guessPinnedVersionFromExistingSpec(deps[alias]),
       pref,
       raw: `${alias}@${pref}`,
diff --git a/packages/supi/test/index.ts b/packages/supi/test/index.ts
index 3e55778413..2e1f7f5dde 100644
--- a/packages/supi/test/index.ts
+++ b/packages/supi/test/index.ts
@@ -8,6 +8,7 @@ import './link'
 import './lockfile'
 import './offline'
 import './packageImportMethods'
+import './parseWantedDependencies.test'
 import './prune'
 import './uninstall'
 import './unlink'
diff --git a/packages/supi/test/parseWantedDependencies.test.ts b/packages/supi/test/parseWantedDependencies.test.ts
new file mode 100644
index 0000000000..6ff54fe088
--- /dev/null
+++ b/packages/supi/test/parseWantedDependencies.test.ts
@@ -0,0 +1,45 @@
+import getSpecFromPackageManifest from 'supi/lib/getSpecFromPackageManifest'
+import promisifyTape from 'tape-promise'
+import tape = require('tape')
+
+const test = promisifyTape(tape)
+
+test('getSpecFromPackageManifest()', (t) => {
+  t.equal(
+    getSpecFromPackageManifest({
+      dependencies: {
+        foo: '3.0.0',
+      },
+      devDependencies: {
+        foo: '2.0.0',
+      },
+      optionalDependencies: {
+        foo: '1.0.0',
+      },
+    }, 'foo'),
+    '1.0.0',
+    'optionalDependencies is first priority'
+  )
+  t.equal(
+    getSpecFromPackageManifest({
+      dependencies: {
+        foo: '3.0.0',
+      },
+      devDependencies: {
+        foo: '2.0.0',
+      },
+    }, 'foo'),
+    '3.0.0',
+    'dependencies is second priority'
+  )
+  t.equal(
+    getSpecFromPackageManifest({
+      devDependencies: {
+        foo: '2.0.0',
+      },
+    }, 'foo'),
+    '2.0.0',
+    'devDependencies is third priority'
+  )
+  t.end()
+})