diff --git a/packages/xod-client/src/project/components/Link.jsx b/packages/xod-client/src/project/components/Link.jsx
index cec643d0..c6e2202b 100644
--- a/packages/xod-client/src/project/components/Link.jsx
+++ b/packages/xod-client/src/project/components/Link.jsx
@@ -2,10 +2,20 @@ import * as R from 'ramda';
 import React from 'react';
 import PropTypes from 'prop-types';
 import classNames from 'classnames';
+import { mapIndexed } from 'xod-func-tools';
 
 import { noop } from '../../utils/ramda';
 import { PIN_RADIUS, LINK_HOTSPOT_SIZE } from '../nodeLayout';
 
+import TooltipHOC from '../../tooltip/components/TooltipHOC';
+
+// :: [Error] -> [ReactNode]
+const renderTooltipContent = mapIndexed((err, idx) => (
+  <div key={idx} className="Tooltip--error">
+    {err.message}
+  </div>
+));
+
 class Link extends React.Component {
   constructor(props) {
     super(props);
@@ -61,33 +71,45 @@ class Link extends React.Component {
     const linkEndRadius = PIN_RADIUS - 3;
 
     return (
-      <g
-        className={cls}
-        id={this.elementId}
-        onClick={this.onClick}
-        style={{ pointerEvents }}
-      >
-        <line
-          stroke="transparent"
-          strokeWidth={LINK_HOTSPOT_SIZE.WIDTH}
-          {...coords}
-        />
-        <line className="line" {...coords} />
-        <circle
-          className="end"
-          cx={coords.x1}
-          cy={coords.y1}
-          r={linkEndRadius}
-          fill="black"
-        />
-        <circle
-          className="end"
-          cx={coords.x2}
-          cy={coords.y2}
-          r={linkEndRadius}
-          fill="black"
-        />
-      </g>
+      <TooltipHOC
+        content={
+          R.isEmpty(this.props.errors)
+            ? null
+            : renderTooltipContent(this.props.errors)
+        }
+        render={(onMouseOver, onMouseMove, onMouseLeave) => (
+          <g
+            className={cls}
+            id={this.elementId}
+            onClick={this.onClick}
+            onMouseOver={onMouseOver}
+            onMouseMove={onMouseMove}
+            onMouseLeave={onMouseLeave}
+            style={{ pointerEvents }}
+          >
+            <line
+              stroke="transparent"
+              strokeWidth={LINK_HOTSPOT_SIZE.WIDTH}
+              {...coords}
+            />
+            <line className="line" {...coords} />
+            <circle
+              className="end"
+              cx={coords.x1}
+              cy={coords.y1}
+              r={linkEndRadius}
+              fill="black"
+            />
+            <circle
+              className="end"
+              cx={coords.x2}
+              cy={coords.y2}
+              r={linkEndRadius}
+              fill="black"
+            />
+          </g>
+        )}
+      />
     );
   }
 }
@@ -98,6 +120,7 @@ Link.propTypes = {
   to: PropTypes.object.isRequired,
   type: PropTypes.string.isRequired,
   dead: PropTypes.bool,
+  errors: PropTypes.arrayOf(PropTypes.instanceOf(Error)),
   isSelected: PropTypes.bool,
   isGhost: PropTypes.bool,
   isOverlay: PropTypes.bool,
@@ -107,6 +130,7 @@ Link.propTypes = {
 
 Link.defaultProps = {
   dead: false,
+  errors: [],
   isSelected: false,
   isGhost: false,
   isOverlay: false,
diff --git a/packages/xod-client/src/project/components/layers/LinksOverlayLayer.jsx b/packages/xod-client/src/project/components/layers/LinksOverlayLayer.jsx
index dd545e10..166d757a 100644
--- a/packages/xod-client/src/project/components/layers/LinksOverlayLayer.jsx
+++ b/packages/xod-client/src/project/components/layers/LinksOverlayLayer.jsx
@@ -20,6 +20,8 @@ const LinksOverlayLayer = ({ links, selection, hidden, onClick }) => (
           from={link.from}
           to={link.to}
           type={link.type}
+          dead={link.dead}
+          errors={link.errors}
           onClick={onClick}
           isSelected={isLinkSelected(selection, link.id)}
         />
diff --git a/packages/xod-client/src/project/selectors.js b/packages/xod-client/src/project/selectors.js
index 39d353f9..d92bfb35 100644
--- a/packages/xod-client/src/project/selectors.js
+++ b/packages/xod-client/src/project/selectors.js
@@ -3,7 +3,7 @@ import { Maybe } from 'ramda-fantasy';
 import { createSelector } from 'reselect';
 
 import * as XP from 'xod-project';
-import { foldMaybe, foldEither } from 'xod-func-tools';
+import { foldMaybe, foldEither, explodeMaybe } from 'xod-func-tools';
 import { createIndexFromPatches } from 'xod-patch-search';
 
 import {
@@ -138,12 +138,12 @@ export const getCurrentPatch = createSelector(
   (patchPath, project) => R.chain(XP.getPatchByPath(R.__, project), patchPath)
 );
 
-// :: Error -> RenderableNode -> RenderableNode
-const addError = R.curry((error, node) =>
+// :: Error -> RenderableNode|RenderableLink -> RenderableNode|RenderableLink
+const addError = R.curry((error, renderableEntity) =>
   R.compose(
     R.over(R.lensProp('errors'), R.append(error)),
     R.unless(R.has('errors'), R.assoc('errors', []))
-  )(node)
+  )(renderableEntity)
 );
 
 // :: Project -> RenderableNode -> RenderableNode
@@ -235,39 +235,37 @@ export const getRenderableNodes = createMemoizedSelector(
 
 // :: State -> StrMap RenderableLink
 export const getRenderableLinks = createMemoizedSelector(
-  [getRenderableNodes, getCurrentPatchLinks],
-  [R.equals, R.equals],
-  (nodes, links) =>
+  [getRenderableNodes, getCurrentPatchLinks, getCurrentPatch, getProject],
+  [R.equals, R.equals, R.equals, R.equals],
+  (nodes, links, curPatch, project) =>
     R.compose(
       addLinksPositioning(nodes),
-      R.map(link => {
-        const inputNodeId = XP.getLinkInputNodeId(link);
-        const outputNodeId = XP.getLinkOutputNodeId(link);
-        const inputPinKey = XP.getLinkInputPinKey(link);
-        const outputPinKey = XP.getLinkOutputPinKey(link);
-
-        const inputNodeIsDead = nodes[inputNodeId].dead;
-        const outputNodeIsDead = nodes[outputNodeId].dead;
-        const inputPinKeyHasDeadType = R.pathEq(
-          [inputNodeId, 'pins', inputPinKey, 'type'],
-          XP.PIN_TYPE.DEAD,
-          nodes
-        );
-        const outputPinKeyHasDeadType = R.pathEq(
-          [outputNodeId, 'pins', outputPinKey, 'type'],
-          XP.PIN_TYPE.DEAD,
-          nodes
-        );
-
-        return R.merge(link, {
-          type: nodes[outputNodeId].pins[outputPinKey].type,
-          dead:
-            inputNodeIsDead ||
-            outputNodeIsDead ||
-            inputPinKeyHasDeadType ||
-            outputPinKeyHasDeadType,
-        });
-      })
+      R.map(link =>
+        R.compose(
+          newLink => {
+            const outputNodeId = XP.getLinkOutputNodeId(link);
+            const outputPinKey = XP.getLinkOutputPinKey(link);
+            return R.assoc(
+              'type',
+              nodes[outputNodeId].pins[outputPinKey].type,
+              newLink
+            );
+          },
+          foldEither(
+            R.pipe(addError(R.__, link), R.assoc('dead', true)),
+            R.identity
+          ),
+          R.map(R.always(link)),
+          XP.validateLinkPins
+        )(
+          link,
+          explodeMaybe(
+            'Imposible error: RenderableLinks will be computed only for current patch',
+            curPatch
+          ),
+          project
+        )
+      )
     )(links)
 );
 
diff --git a/packages/xod-project/src/project.js b/packages/xod-project/src/project.js
index 4ae83492..7f0f47d6 100644
--- a/packages/xod-project/src/project.js
+++ b/packages/xod-project/src/project.js
@@ -475,15 +475,14 @@ const checkLinkPin = def(
 /**
  * Checks project for existence of patches and pins that used in link.
  *
- * @private
- * @function checkPinKeys
+ * @function validateLinkPins
  * @param {Link} link
  * @param {Patch} patch
  * @param {Project} project
  * @returns {Either<Error|Patch>}
  */
-const checkPinKeys = def(
-  'checkPinKeys :: Link -> Patch -> Project -> Either Error Patch',
+export const validateLinkPins = def(
+  'validateLinkPins :: Link -> Patch -> Project -> Either Error Patch',
   (link, patch, project) => {
     const checkInputPin = checkLinkPin(
       Link.getLinkInputNodeId,
@@ -548,7 +547,7 @@ export const validatePatchContents = def(
         R.compose(
           R.map(R.always(patch)),
           R.sequence(Either.of),
-          R.map(checkPinKeys(R.__, patch, project))
+          R.map(validateLinkPins(R.__, patch, project))
         )
       ),
       Patch.listLinks