diff --git a/command/cliconfig/provider_installation.go b/command/cliconfig/provider_installation.go
index 28ca74b2c6..3d4919950c 100644
--- a/command/cliconfig/provider_installation.go
+++ b/command/cliconfig/provider_installation.go
@@ -42,7 +42,12 @@ func decodeProviderInstallationFromConfig(hclFile *hclast.File) ([]*ProviderInst
 		if block.Keys[0].Token.Value() != "provider_installation" {
 			continue
 		}
-		if block.Assign.Line != 0 {
+		// HCL only tracks whether the input was JSON or native syntax inside
+		// individual tokens, so we'll use our block type token to decide
+		// and assume that the rest of the block must be written in the same
+		// syntax, because syntax is a whole-file idea.
+		isJSON := block.Keys[0].Token.JSON
+		if block.Assign.Line != 0 && !isJSON {
 			// Seems to be an attribute rather than a block
 			diags = diags.Append(tfdiags.Sourceless(
 				tfdiags.Error,
@@ -51,7 +56,7 @@ func decodeProviderInstallationFromConfig(hclFile *hclast.File) ([]*ProviderInst
 			))
 			continue
 		}
-		if len(block.Keys) > 1 {
+		if len(block.Keys) > 1 && !isJSON {
 			diags = diags.Append(tfdiags.Sourceless(
 				tfdiags.Error,
 				"Invalid provider_installation block",
@@ -61,13 +66,22 @@ func decodeProviderInstallationFromConfig(hclFile *hclast.File) ([]*ProviderInst
 
 		pi := &ProviderInstallation{}
 
-		// Because we checked block.Assign was unset above we can assume that
-		// we're reading something produced with block syntax and therefore
-		// it will always be an hclast.ObjectType.
-		body := block.Val.(*hclast.ObjectType)
+		body, ok := block.Val.(*hclast.ObjectType)
+		if !ok {
+			// We can't get in here with native HCL syntax because we
+			// already checked above that we're using block syntax, but
+			// if we're reading JSON then our value could potentially be
+			// anything.
+			diags = diags.Append(tfdiags.Sourceless(
+				tfdiags.Error,
+				"Invalid provider_installation block",
+				fmt.Sprintf("The provider_installation block at %s must not be introduced with an equals sign.", block.Pos()),
+			))
+			continue
+		}
 
 		for _, methodBlock := range body.List.Items {
-			if methodBlock.Assign.Line != 0 {
+			if methodBlock.Assign.Line != 0 && !isJSON {
 				// Seems to be an attribute rather than a block
 				diags = diags.Append(tfdiags.Sourceless(
 					tfdiags.Error,
@@ -76,7 +90,7 @@ func decodeProviderInstallationFromConfig(hclFile *hclast.File) ([]*ProviderInst
 				))
 				continue
 			}
-			if len(methodBlock.Keys) > 1 {
+			if len(methodBlock.Keys) > 1 && !isJSON {
 				diags = diags.Append(tfdiags.Sourceless(
 					tfdiags.Error,
 					"Invalid provider_installation method block",
@@ -84,7 +98,19 @@ func decodeProviderInstallationFromConfig(hclFile *hclast.File) ([]*ProviderInst
 				))
 			}
 
-			methodBody := methodBlock.Val.(*hclast.ObjectType)
+			methodBody, ok := methodBlock.Val.(*hclast.ObjectType)
+			if !ok {
+				// We can't get in here with native HCL syntax because we
+				// already checked above that we're using block syntax, but
+				// if we're reading JSON then our value could potentially be
+				// anything.
+				diags = diags.Append(tfdiags.Sourceless(
+					tfdiags.Error,
+					"Invalid provider_installation method block",
+					fmt.Sprintf("The items inside the provider_installation block at %s must all be blocks.", block.Pos()),
+				))
+				continue
+			}
 
 			methodTypeStr := methodBlock.Keys[0].Token.Value().(string)
 			var location ProviderInstallationLocation
diff --git a/command/cliconfig/provider_installation_test.go b/command/cliconfig/provider_installation_test.go
index 0712e0e9f6..5eb0b412f3 100644
--- a/command/cliconfig/provider_installation_test.go
+++ b/command/cliconfig/provider_installation_test.go
@@ -8,38 +8,42 @@ import (
 )
 
 func TestLoadConfig_providerInstallation(t *testing.T) {
-	got, diags := loadConfigFile(filepath.Join(fixtureDir, "provider-installation"))
-	if diags.HasErrors() {
-		t.Errorf("unexpected diagnostics: %s", diags.Err().Error())
-	}
+	for _, configFile := range []string{"provider-installation", "provider-installation.json"} {
+		t.Run(configFile, func(t *testing.T) {
+			got, diags := loadConfigFile(filepath.Join(fixtureDir, configFile))
+			if diags.HasErrors() {
+				t.Errorf("unexpected diagnostics: %s", diags.Err().Error())
+			}
 
-	want := &Config{
-		ProviderInstallation: []*ProviderInstallation{
-			{
-				Methods: []*ProviderInstallationMethod{
-					{
-						Location: ProviderInstallationFilesystemMirror("/tmp/example1"),
-						Include:  []string{"example.com/*/*"},
-					},
-					{
-						Location: ProviderInstallationNetworkMirror("https://tf-Mirror.example.com/"),
-						Include:  []string{"registry.terraform.io/*/*"},
-						Exclude:  []string{"registry.Terraform.io/foobar/*"},
-					},
-					{
-						Location: ProviderInstallationFilesystemMirror("/tmp/example2"),
-					},
+			want := &Config{
+				ProviderInstallation: []*ProviderInstallation{
 					{
-						Location: ProviderInstallationDirect,
-						Exclude:  []string{"example.com/*/*"},
+						Methods: []*ProviderInstallationMethod{
+							{
+								Location: ProviderInstallationFilesystemMirror("/tmp/example1"),
+								Include:  []string{"example.com/*/*"},
+							},
+							{
+								Location: ProviderInstallationNetworkMirror("https://tf-Mirror.example.com/"),
+								Include:  []string{"registry.terraform.io/*/*"},
+								Exclude:  []string{"registry.Terraform.io/foobar/*"},
+							},
+							{
+								Location: ProviderInstallationFilesystemMirror("/tmp/example2"),
+							},
+							{
+								Location: ProviderInstallationDirect,
+								Exclude:  []string{"example.com/*/*"},
+							},
+						},
 					},
 				},
-			},
-		},
-	}
+			}
 
-	if diff := cmp.Diff(want, got); diff != "" {
-		t.Errorf("wrong result\n%s", diff)
+			if diff := cmp.Diff(want, got); diff != "" {
+				t.Errorf("wrong result\n%s", diff)
+			}
+		})
 	}
 }
 
diff --git a/command/cliconfig/testdata/provider-installation.json b/command/cliconfig/testdata/provider-installation.json
new file mode 100644
index 0000000000..826d68d470
--- /dev/null
+++ b/command/cliconfig/testdata/provider-installation.json
@@ -0,0 +1,19 @@
+{
+  "provider_installation": {
+    "filesystem_mirror": [{
+      "path": "/tmp/example1",
+      "include": ["example.com/*/*"]
+    }],
+    "network_mirror": [{
+      "url": "https://tf-Mirror.example.com/",
+      "include": ["registry.terraform.io/*/*"],
+      "exclude": ["registry.Terraform.io/foobar/*"]
+    }],
+    "filesystem_mirror": [{
+      "path": "/tmp/example2"
+    }],
+    "direct": [{
+      "exclude": ["example.com/*/*"]
+    }]
+  }
+}